CN113337238B - High-strength light reversible adhesive, preparation method and application - Google Patents

Abstract

The invention discloses a high-strength photo-reversible adhesive, a preparation method and application thereof. The invention firstly epoxidizes the raw material of the compound containing the anthryl to prepare the epoxidizing product containing the anthracene, then mixes the epoxidizing product with the mercapto-terminated alcohol compound and the accelerant, and carries out ring opening at room temperature to prepare the double-end hydroxyl compound containing the anthryl side chain. An isocyanate compound at the two ends and polycaprolactone at the two ends are added with an organic tin catalyst to carry out chain extension reaction to form a chain extension isocyanate compound at the two ends with larger molecular weight. And finally, reacting the chain-extended double-end isocyanate compound with a double-end hydroxyl compound containing an anthracene-based side chain and a double-end hydroxyl compound not containing the anthracene-based side chain, and adding an organic tin catalyst for catalytic reaction to obtain the high-strength photo-reversible adhesive. The adhesive is subjected to a [4+4] cycloaddition reaction under the irradiation of ultraviolet light of 350-405 nm, and is cured; and (3) carrying out de-crosslinking under the irradiation of ultraviolet light with the wavelength of less than 300 nm.

Description

High-strength light reversible adhesive, preparation method and application

Technical Field

The invention relates to the technical field of adhesives, and further relates to a high-strength photo-reversible adhesive, a preparation method and application thereof.

Background

The adhesive is a material capable of firmly bonding two base materials together, is widely applied to various military and civil fields, and is an essential material for the industries of automobiles, biomedicine, construction and aerospace. To save cost and reduce environmental pollution, the design and application of reversible adhesives are needed.

Currently, reversible adhesives are based primarily on a thermoreversible mechanism, while photoinduced approaches have been receiving attention for their non-contact initiation, non-directional initiation, and rapid, simple operation. Photoisomerization of azobenzene is a way to prepare photo-induced reversible adhesives. The substrates containing successive azobenzene sequences are bonded together in solid form under irradiation with visible light and liquefied under irradiation with ultraviolet light to effect debonding. Due to the limitation of the motion capability of the chain segment, the method is only suitable for thermoplastic adhesives and is easy to creep deformation.

Tristan Harper et al studied a light-induced cured acrylate wet surface adhesive containing pendant anthracene groups, but no study on the reversible properties of the adhesive was included in the report. (T.Harper, R.Slegers, I.Pramudya, H.Chung, Single-phase photo-cross-linked adhesive for precise control of adhesive strength, ACS appl.Mater.Interfaces.2017, 9, 1830-1839.) other researchers have also explored the use of derivatives of anthracene in reversible thermosetting adhesives, respectively. However, the application of these adhesives, in addition to being photo-induced during the cured bond, still relies on heat assistance during the release process.

It is of interest to design a process for achieving adhesion and debonding by photoinitiation, which maximizes the advantages of photoinitiation. Researchers have studied the use of light-induced reversible thermosetting adhesives during the bonding and debonding processes. However, the prior research results still have a problem that when the glass transition temperature of the reaction product is obviously higher than the ambient temperature, the polymer chain segment is frozen in the reaction process, so that the reaction efficiency is low, and even the reaction can not be carried out. Although systems with lower glass transition temperatures ensure complete curing, the cured products are in a highly elastic state at room temperature. Both of the above-mentioned cases adversely affect the bonding strength of the photo-induced reversible adhesive.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a high-strength photo-reversible adhesive, a preparation method and application thereof. The adhesive contains anthracene group and polycaprolactone crystal chain segment, and is a light-induced reversible adhesive with excellent bonding performance. Firstly, epoxidizing a compound raw material containing anthracene group to prepare an epoxidizing product containing anthracene, then mixing the epoxidizing product with a mercapto-terminated alcohol compound and an accelerant, and carrying out ring opening at room temperature to prepare a double-end hydroxyl compound containing anthracene group side chains. An isocyanate compound at the two ends and polycaprolactone at the two ends of hydroxyl are added with an organic tin catalyst to carry out chain extension reaction to form a chain extension isocyanate compound at the two ends with larger molecular weight. And finally, reacting the chain-extended double-ended isocyanate compound with a double-ended hydroxyl compound containing an anthracene-based side chain and a double-ended hydroxyl compound not containing the anthracene-based side chain, and adding an organic tin catalyst for catalytic reaction to obtain a linear polyurethane structure compound containing the anthracene-based side chain and a polycaprolactone crystal chain segment, namely the high-strength photo-reversible adhesive. The adhesive is subjected to a [4+4] cycloaddition reaction under the irradiation of ultraviolet light of 350-405 nm, and is cured; and (3) carrying out crosslinking under the irradiation of ultraviolet light with the wavelength of less than 300 nm.

It is an object of the present invention to provide a high-strength photo-reversible adhesive.

The adhesive comprises the following structure:

0< q < 8; 0< p < 7; 0< n < 8; 0< m < 6; and p, q, n, m are integers;

wherein, the first and the second end of the pipe are connected with each other,

a is

B is as follows:

a is an integer between 19 and 40, including endpoints 19 and 40;

d is as follows:

b is an integer between 4 and 6, including endpoints 4 and 6;

r is

The adhesive can react under the irradiation of ultraviolet light with different wavelengths as follows:

curing under the irradiation of ultraviolet light of 350-405 nm; heating is preferably carried out before irradiation with ultraviolet light to bring the adhesive into a molten state; the irradiation time can be determined according to actual conditions and is generally 5-10 minutes;

de-crosslinking under the irradiation of ultraviolet light of less than 300 nm; the irradiation time is determined according to the actual situation, and is generally not less than 2 hours;

the invention also aims to provide a preparation method of the high-strength photo-reversible adhesive.

The method comprises the following steps:

dissolving an anthracene-based compound in a solvent A, then adding an epoxy compound, alkali and a phase transfer catalyst, and stirring for reaction to obtain an anthracene-based epoxidation product;

step (2), dissolving the epoxidation product containing the anthracene group obtained in the step (1) in a solvent B, adding a thiol-terminated compound and an accelerator, and stirring for reaction to obtain a hydroxyl-terminated compound containing an anthracene group side chain;

dissolving the isocyanate-terminated compound and the polycaprolactone with double hydroxyl groups in a solvent C, adding an organic tin catalyst, and stirring for reaction to generate a chain-extended isocyanate-terminated compound;

and (4) dissolving the chain-extended double-ended isocyanate compound, the double-ended hydroxyl compound containing the anthracene-based side chain and the double-ended hydroxyl compound not containing the anthracene-based side chain in a solvent D, adding an organic tin catalyst, and stirring for reaction to obtain the high-strength photo-reversible adhesive (the compound with the linear polyurethane structure and containing the anthracene-based side group and the polycaprolactone crystal chain segment).

In a preferred embodiment of the present invention,

in the step (1), the step (c),

the anthracene-based compound is at least one selected from 9-anthracene methanol and 1- (9-anthracene-based) ethanol; preferably 9-anthracenemethanol;

the epoxy compound is selected from epoxy halogen compounds; preferably epichlorohydrin;

the alkali is selected from sodium hydroxide or potassium hydroxide; preferably sodium hydroxide;

the phase transfer catalyst is selected from tetramethylamine halogen compounds; tetramethyl ammonium bromide is preferred;

the solvent A is a non-polar solvent; toluene is preferred;

the molar ratio of the anthracene-based compound to the epoxy compound to the base to the phase transfer catalyst is 1: (5-10): (2-4): (0.01-0.03);

the molar ratio of the anthracene-based compound to the solvent A is 1: 20-1: 30;

the stirring reaction temperature is 60-70 ℃, and the stirring reaction time is 3-6 h.

In a preferred embodiment of the present invention,

in the step (2),

the solvent B is a non-polar solvent; toluene is preferred;

the mercapto-terminated alcohol compound is at least one selected from 2-mercaptoethanol, 3-mercapto-1-propanol and 4-mercapto-1-butanol; preferably 2-mercaptoethanol;

the accelerator is selected from tertiary amine compounds; 2, 4, 6-tris (dimethylaminomethyl) phenol (DMP-30) is preferably selected; the amount of the accelerant is 0.5 to 1 weight percent of the total weight of the anthracene-based epoxidation product and the end mercapto alcohol compound;

the molar ratio of the anthracene-based epoxide to the solvent B is 1: 20-1: 30;

the molar ratio of the anthracene-group-containing epoxidation product to the mercapto-terminated alcohol compound is 1: 1-1: 1.1;

the stirring reaction temperature is 20-30 ℃, and the stirring reaction time is 2-3 h.

In a preferred embodiment of the present invention,

in the step (3), the step (c),

the double-end isocyanate group compound is selected from one of 4, 4-diphenylmethane diisocyanate, 4, 4-dicyclohexylmethane diisocyanate and hexamethylene diisocyanate; preferably 4, 4-dicyclohexylmethane diisocyanate;

the weight average molecular weight of the polycaprolactone with double hydroxyl groups at the end is 2000-4000, and the raw material with the weight average molecular weight of 2000 is preferably selected;

the solvent C is a polar solvent; preferably methyl isobutyl ketone;

the organic tin catalyst is dibutyltin dilaurate; the dosage of the catalyst is 0.5 to 1 weight percent of the total weight of the isocyanate-terminated compound and the hydroxyl-terminated polycaprolactone;

the molar ratio of the hydroxyl-terminated polycaprolactone to the solvent C is 1: 30-1: 40;

the molar ratio of the double-end isocyanate group compound to the double-end hydroxyl group polycaprolactone is 2: 1-2.1: 1;

the stirring reaction temperature is 70-80 ℃, and the stirring reaction time is 2-3 h.

In a preferred embodiment of the present invention,

in the step (4), the step (c),

the double-end hydroxyl compound without the anthryl side chain is selected from one of methylene glycol such as 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol and the like; preferably 1, 4-butanediol;

the solvent D is a polar solvent; preferably methyl isobutyl ketone;

the molar ratio of the isocyanate group to the hydroxyl group is 1: 1-1.1: 1;

the molar ratio of the double-end hydroxyl compound containing the anthryl side chain to the double-end hydroxyl compound not containing the anthryl side chain is 1: (0.25 to 4);

the organic tin catalyst is dibutyltin dilaurate; the dosage of the catalyst is 0.5 to 1 weight percent of the total weight of the chain-extended double-end isocyanate-based compound, the double-end hydroxyl compound containing the anthryl side chain and the double-end hydroxyl compound not containing the anthryl side chain;

the molar ratio of the chain-extended double-end isocyanate-based compound to the solvent D is 1: 30-1: 40;

the stirring reaction temperature is 70-80 ℃, and the stirring reaction time is 2-3 h.

In a further preferred embodiment of the invention,

centrifuging, extracting, rotary evaporating and drying the anthracene-based-containing epoxidation product obtained in the step (1); wherein the extraction solvent is at least one selected from toluene, methyl isobutyl ketone and ethyl acetate;

the centrifugation, extraction, rotary evaporation and drying operations can be carried out in any conventional equipment capable of carrying out the operations.

And (3) removing the solvent from the product obtained in the steps (2), (3) and (4) in vacuum heating equipment, wherein the heating temperature is 90-100 ℃, and the heating time is 2-3 h.

The invention also aims to provide the high-strength light reversible adhesive prepared by the method.

The fourth purpose of the invention is to provide the application of the high-intensity light reversible adhesive in the light-transmitting base material.

The adhesive is suitable for bonding various light-transmitting base materials, in particular for bonding quartz glass.

Compared with the prior art, the invention has the following advantages:

1. the anthracene group in the adhesive has stronger reactivity and operability compared with other light-induced reversible reaction groups such as coumarin and disulfide bond; compared with a photoisomerization group such as azobenzene, the anthracene group can be applied to thermosetting polymers and has a stable cross-linking structure, so that stronger bonding strength and stability are provided.

2. The invention constructs a semi-crystalline photo-induced reversible adhesive, and the crystalline chain segment improves the bonding strength and the creep resistance on the basis of a cross-linked network with low glass transition temperature; the crosslinked segment in the amorphous phase still ensures smooth progress of the reversible curing reaction at a low glass transition temperature.

The high-strength photo-reversible adhesive containing the anthryl group and the polycaprolactone crystal chain segment has the advantages that due to the existence of the cross-linking points, the arrangement of the chain segment is hindered, so that the cross-linking chain segment exists basically in an amorphous phase form, and under the lower glass transition temperature, the [4+4] cycloaddition reaction of the anthryl can be induced under 350-405 nm ultraviolet light, so that cross-linking is realized, and stronger bonding force is provided; at the wavelength of ultraviolet light (less than 300nm), the depolymerization of cycloaddition product can be induced, and the decrosslinking occurs, so that the adhesive force is reduced. The photoinitiation reaction has the advantage of quick reaction, the chain segment of the molten mass can be quickly solidified into a film before being limited by crystallization, and the illumination time of ultraviolet light is 5-10 min. Meanwhile, the non-crosslinked chain segment still has stronger crystallization capacity, and the existence of the crystalline chain segment plays roles of strengthening and creep resistance on the basis of a low glass transition temperature system. The photo-reversible adhesive provided by the invention has excellent bonding performance, the tensile shear strength can reach 3.8MPa, and the photo-reversible adhesive is superior to other currently reported photo-reversible adhesives; the crosslinked structure is lost after photolysis and the re-derived linear structure can be easily debonded by solvent. Polar solvent is selected in the de-binding process, and acetone is preferably selected in the experiment; the solvent treatment time is 5-10 min; after the solvent treatment no more polymer remains on the substrate.

Drawings

FIG. 1 is an infrared spectrum of 9-anthracenemethanol, 9-anthracenemethanol epoxide and the double-terminal hydroxyl compound having an anthracenyl side chain of example 1, wherein curve 1a is an infrared spectrum of 9-Anthracenemethanol (AM), curve 1b is an infrared spectrum of 9-Anthracenemethanol Epoxide (AER), and curve 1c is an infrared spectrum of the double-terminal hydroxyl compound having an anthracenyl side chain (AERMT);

FIG. 2 is a graph of AER and AERMT obtained in example 1¹H NMR spectrum with curve 2a for 9-Anthracenemethanol (AM)¹H NMR spectrum, curve 2b for 9-Anthracenemethylol Epoxide (AER)¹H NMR spectrum;

FIG. 3 is a graph of the AER obtained in example 1¹³C NMR spectrum;

FIG. 4 is a graph of AERMT obtained in example 1¹³C NMR spectrum;

FIG. 5 shows that the high molecular weight isocyanate-terminated compound (PCL/HMDI) generated by the chain extension reaction in example 1 reacts with hydroxyl-terminated compound (AERMT) containing anthracene-based side chain and 1, 4-Butanediol (BD) to obtain compound (APU) with linear polyurethane structure containing anthracene-based side chain and polycaprolactone crystal segment; wherein curve 5a is the infrared spectrum of PCL/HMDI, and curve 5b is the infrared spectrum of APU;

FIG. 6 is a diagram of the phase structure of APU obtained in example 1 monitored by XRD;

FIG. 7 is a graph showing the retention time of APU molecules obtained in example 1 in a gel permeation chromatography column monitored by GPC;

FIG. 8 is a DSC cooling-heating scan of the melt of APU obtained in example 1 and maintained at room temperature (25 ℃) for 20min during cooling, characterizing the crystallization rate at room temperature;

FIG. 9 is a viscosity-temperature curve of a melt of the APU obtained in example 1;

FIG. 10 is a graph showing the light curing process of the APU obtained in example 1, followed by an ultraviolet-visible spectrophotometer for a total of 5 minutes;

FIG. 11 is a DSC warming scan curve (0-80 ℃) of the crystals of the APU obtained in example 1, wherein a curve 11a is the APU warming scan curve before curing, and a curve 11b is the APU warming scan curve after curing;

FIG. 12 is a DSC heating scanning curve (-65-10 ℃) of the crystal of the APU obtained in example 1, wherein curve 12a is the APU heating scanning curve before curing, and curve 12b is the APU heating scanning curve after curing;

FIG. 13 is a tensile shear test curve of the APU obtained in example 1, 13a is a tensile shear test result of the APU obtained in example 1 after crosslinking and crystallization, and 13b is a tensile shear test result of the APU obtained in example 1 after crosslinking and crystallization and then light-induced decrosslinking.

FIG. 14 is an infrared spectrum of 9-anthracenemethanol, 9-anthracenemethanol epoxide and the double-terminal hydroxyl compound containing an anthracenyl side chain of example 2, wherein curve 14a is the infrared spectrum of 9-Anthracenemethanol (AM), curve 14b is the infrared spectrum of 9-Anthracenemethanol Epoxide (AER), and curve 14c is the infrared spectrum of the double-terminal hydroxyl compound containing an anthracenyl side chain (AERMT);

FIG. 15 is a graph of AER and AERMT obtained in example 2¹H NMR spectrum with curve 15a for 9-Anthracenemethanol (AM)¹H NMR spectrum, curve 15b for 9-Anthracenemethylol Epoxide (AER)¹H NMR spectrum;

FIG. 16 is a graph of AER obtained in example 2¹³C NMR spectrum;

FIG. 17 is a graph of AERMT obtained in example 2¹³C NMR spectrum;

FIG. 18 shows that the high molecular weight isocyanate-terminated compound (PCL/HMDI) generated by the chain extension reaction in example 2 reacts with hydroxyl-terminated compound (AERMT) containing anthracene-based side chain and 1, 4-Butanediol (BD) to obtain compound (APU) with linear polyurethane structure containing anthracene-based side chain and polycaprolactone crystal segment; wherein curve 18a is the infrared spectrum of PCL/HMDI, and curve 18b is the infrared spectrum of APU;

FIG. 19 is a phase diagram of APU monitoring obtained in example 2 using XRD;

FIG. 20 is a graph showing the retention time of APU molecules of example 2 in a gel permeation chromatography column monitored by GPC;

FIG. 21 is a DSC cooling-heating scan of the melt of APU obtained in example 2 and maintained at room temperature (25 ℃) for 20min during cooling, characterizing the crystallization rate at room temperature;

FIG. 22 is a viscosity-temperature curve of a melt of the APU obtained in example 2;

FIG. 23 is a graph showing the UV-visible spectrophotometer tracking the light curing process of the APU obtained in example 2, wherein the light irradiation time is 5 minutes;

FIG. 24 is a DSC heating scan curve (0-80 ℃) of the crystals of the APU obtained in example 2, wherein a curve 24a is the APU heating scan curve before curing, and a curve 24b is the APU heating scan curve after curing;

FIG. 25 is a DSC heating scan curve (-65-10 ℃) of the crystal of the APU obtained in example 2, wherein a curve 25a is the APU heating scan curve before curing, and a curve 25b is the APU heating scan curve after curing;

fig. 26 is a tensile shear test curve of APU obtained in example 2, 26a is a tensile shear test result of APU obtained in example 2 after cross-linking and crystallization, and 26b is a tensile shear test result of APU obtained in example 2 after cross-linking and crystallization and then light-induced de-cross-linking.

FIG. 27 is an infrared spectrum of 9-anthracenemethanol, 9-anthracenemethanol epoxide and the double-terminal hydroxyl compound containing an anthracenyl side chain of example 3, wherein curve 27a is the infrared spectrum of 9-Anthracenemethanol (AM), curve 27b is the infrared spectrum of 9-Anthracenemethanol Epoxide (AER), and curve 27c is the infrared spectrum of the double-terminal hydroxyl compound containing an anthracenyl side chain (AERMT);

FIG. 28 is a graph of AER and AERMT obtained in example 3¹H NMR spectrum with curve 28a for 9-Anthracenemethanol (AM)¹H NMR spectrum, curve 28b for 9-Anthracenemethylol Epoxide (AER)¹H NMR spectrum;

FIG. 29 is a graph of AER obtained in example 3¹³C NMR spectrum;

FIG. 30 is a graph of AERMT obtained in example 3¹³C NMR spectrum;

FIG. 31 shows that the high molecular weight isocyanate-terminated compound (PCL/HMDI) generated by the chain extension reaction obtained in example 3 reacts with hydroxyl-terminated compound (AERMT) containing anthracene-based side chain and 1, 4-Butanediol (BD) to obtain compound (APU) with linear polyurethane structure containing anthracene-based side chain and polycaprolactone crystal segment; wherein the curve 31a is the infrared spectrum of PCL/HMDI, and the curve 31b is the infrared spectrum of APU;

FIG. 32 is a phase diagram of APU monitoring obtained in example 3 using XRD;

FIG. 33 is a graph showing the retention time of APU molecules obtained in example 3 in a gel permeation chromatography column monitored by GPC;

FIG. 34 is a DSC cooling-heating scan of the melt of APU obtained in example 3 and incubated at room temperature (25 ℃) for 20min during cooling, characterizing the crystallization rate at room temperature;

FIG. 35 is a viscosity-temperature curve of a melt of the APU obtained in example 3;

FIG. 36 is a graph showing the UV-visible spectrophotometer tracking the light curing process of the APU obtained in example 3, wherein the light irradiation time is 10 minutes;

FIG. 37 is a DSC heating scan curve (0-80 ℃) of the crystals of the APU obtained in example 3, wherein a curve 37a is the APU heating scan curve before curing, and a curve 37b is the APU heating scan curve after curing;

FIG. 38 is a DSC heating scan curve (-65-10 ℃) of the crystal of the APU obtained in example 3, wherein a curve 38a is the APU heating scan curve before curing, and a curve 38b is the APU heating scan curve after curing;

fig. 39 is a tensile shear test curve of the APU obtained in example 3, 39a is a tensile shear test result of the APU obtained in example 3 after crosslinking and crystallization, and 39b is a tensile shear test result of the APU obtained in example 3 after crosslinking and crystallization and then light-induced decrosslinking.

Detailed Description

While the present invention will be described in detail and with reference to the specific embodiments thereof, it should be understood that the following detailed description is only for illustrative purposes and is not intended to limit the scope of the present invention, as those skilled in the art will appreciate numerous insubstantial modifications and adaptations of the invention in light of the above teachings.

The test instruments and test conditions used in the examples were as follows:

FTIR: bruker Alpha FTIR adopts a KBr tablet pressing method and is arranged at 4000-400 cm^-1Within a wave number range of 4cm^-1At a resolution of (c).

NMR: nuclear magnetic resonance spectroscopy (¹H-NMR and¹³C-NMR) at room temperature using CDCl₃The solvent was used on a Bruker AV400MHz NMR spectrometer (Germany).

XRD: the diffraction peaks of the crystalline and amorphous regions of the sample were collected at room temperature using an X-ray diffractometer (Netherlands) at 40kV,40mA, Cu Ka radiation.

Viscosity: heating at 25-150 deg.C at 4 deg.C/min and shear rate of 50s^-1The viscosity was measured using a rheometer (MCR-301, Anton Paar) and a parallel plate tool.

GPC: a Waters 1525 instrument was used, equipped with a Waters 2414RI detector, tetrahydrofuran as the mobile phase (flow rate: 0.6 ml/min; column temperature: 35 ℃).

UV-vis: UV-vis spectroscopy was performed by a Shimadzu UV-2550 spectrometer in absorption mode. The solid state sample test method was used.

DSC: in a device equipped with RCS 90TA Instruments Q20 on Cooling System, N₂Atmosphere (50 ml. min)^-1) Next, DSC tests were performed on the original, uncrosslinked, and re-crosslinked networks. All samples were heated from-50 ℃ to 100 ℃ at a heating rate of 10 ℃/min.

Tensile shear test: tensile shear strength testing was performed at room temperature using a SANS UTM5205XHD test rig. The bonding substrates include quartz glass and PE films using a single lap shear test method. The moving speed of the sample holder was set to 10 mm/min.

The sources of the compounds used in the examples are as follows:

name of medicine	Manufacturer of the product
		9-Anthracene methanol	Annagi reagent Ltd
Epoxy chloropropane	Tianjin Fuchen (China) chemical Co., Ltd
		Sodium hydroxide	Beijing chemical plant (China)
Tetramethyl ammonium bromide	Beijing chemical plant (China)
		Toluene	Tianjin Fuchen (China) chemical Co., Ltd
Methyl isobutyl ketone	Tianjin Fuchen (China) chemical Co., Ltd
		2-mercaptoethanol	SHANGHAI MACKLIN BIOCHEMICAL Co.,Ltd.
2.4, 6-tris (dimethylaminomethyl) phenol	San Diego Bioruler, USA
		Polycaprolactone diol	TIANJIN HEOWNS BIOCHEMISTRY TECHNOLOGY Co.,Ltd.
Dibutyl tin dilaurate	SHANGHAI MACKLIN BIOCHEMICAL Co.,Ltd.
		1, 4-butanediol	Tianjin Fuchen (China) chemical Co., Ltd
4, 4-dicyclohexylmethane diisocyanate	SHANGHAI MACKLIN BIOCHEMICAL Co.,Ltd.
		Distilled water	Self-made
Quartz glass sheet	Weddar quartz, Living Ltd, Living Hongyun, China

Example 1

The structural formula of the adhesive is as follows:

0< q < 8; 0< p < 7; 0< n < 8; 0< m < 6; and p, q, n, m are integers; wherein the content of the first and second substances,

a is

B is as follows:

a＝19

d is as follows:

b＝4

r is

The preparation method comprises the following steps:

1) preparation of anthracene-containing epoxidation product: dissolving 1mol of 9-Anthracene Methanol (AM) raw material in 25mol of nonpolar solvent toluene, adding 8mol of epichlorohydrin, keeping the temperature in a water bath at 65 ℃, and then adding 3mol of sodium hydroxide and 0.02mol of tetramethyl ammonium bromide (TMAB). Stirring and reacting for 4h under heat preservation, and obtaining an anthracene-based epoxidation product, namely 9-anthracene methanol epoxide (AER), through centrifugation, toluene extraction, rotary evaporation and vacuum drying;

2) preparation of double-terminal hydroxyl compound containing anthracene-based side chain: mixing 0.5mol of 9-anthracene methanol epoxide prepared in the step 1) with 0.525mol of mercaptoethanol, dissolving in 12.5mol of toluene, adding DMP-30 accelerator accounting for 0.75% of the mass fraction, uniformly stirring, reacting at 25 ℃ for 2.5h, and performing rotary evaporation and vacuum drying to obtain an anthracene group-containing epoxidation product (AERMT);

3) preparation of chain-extended, double-ended isocyanate-based compounds: 0.041mol of 4, 4-dicyclohexylmethane diisocyanate (HMDI) and 0.02mol of bis-hydroxy-terminated polycaprolactone (M)_w2000), namely polycaprolactone diol (PCL-2OH), is dissolved in 0.7mol of methyl isobutyl ketone solvent, dibutyltin dilaurate (DBTDL) catalyst is added in an amount of 0.75% by mass, after uniform stirring, the reaction is carried out for 2.5h at 75 ℃, and a chain-extended, double-ended isocyanate compound (PCL/HMDI) is obtained by rotary evaporation and vacuum drying;

4) the preparation of the linear polyurethane structure compound containing anthracene side group and polycaprolactone crystal chain segment comprises the following steps: 0.021mol of PCL/HMDI, 0.01mol of AERMT and 0.01mol of 1, 4-Butanediol (BD) are dissolved in 0.7mol of methyl isobutyl ketone solvent, the molar ratio of isocyanate groups to hydroxyl groups is 1.05:1, dibutyltin dilaurate (DBTDL) catalyst is added according to the mass fraction of 0.75%, and the mixture is stirred uniformly and then reacted at 75 ℃ for 2.5 hours to obtain the high-strength APU (APU-1).

5) And (3) curing: preheating the adhesive prepared in the step 4) at 60 ℃ for 1min in advance to melt the adhesive, fixing two quartz glass substrates, applying a rated pre-pressure (20KPa), and then transferring the melt to 365nm wavelength ultraviolet light (40W) to irradiate for 5min to solidify the melt to obtain the solidified adhesive (CL-APU-1) containing the anthryl group and the polycaprolactone crystalline chain segment.

The obtained cured adhesive was left at room temperature (25 ℃) for 2 hours to be fully crystallized, and subjected to a tensile shear test, and the adhesion strength to quartz glass was measured to be 3.8MPa (fig. 13 a); after the adhesive is irradiated for 2 hours under 254nm ultraviolet light (8W), the intensity of the adhesive after photodegradation is 2.1MPa (figure 13b), and the adhesive still has certain bonding strength because the crystal chain segment still exists. The photolyzed adhesive was soaked in acetone for 10 minutes, and the linear polyurethane polymer recovered after photolysis was dissolved in acetone and no more polymer remained on the substrate.

And (3) testing and characterizing:

infrared Spectrum characterization of AER and AERMT

FIG. 1 shows a schematic view of a liquid crystal display device of example 1The infrared spectra of 9-Anthracenemethanol (AM), 9-Anthracenemethanol Epoxide (AER) and double-terminal hydroxyl compound (AERMT) containing anthracenyl side chain, wherein 1a is AM at 3400cm^-1The nearby broad peak is attributed to the vibration of-OH, and after the reaction, the disappearance of the absorption can be observed, indicating that-OH is completely consumed in the reaction; 1b is the spectrum of AER at 913cm^-1The absorption at (a) represents the characteristic absorption of the epoxy group, indicating that the epoxidation reaction between epichlorohydrin and-OH groups has been successfully carried out. 1c is the spectrum of AERMT at 913cm^-1The absorption peak at (1) disappears, 3400cm^-1The reappearance of a broad peak near the ring opening reaction due to-OH proves that the ring opening reaction of the epoxy group forms-OH.

NMR characterization of AER and AERMT

To further confirm the structure, we performed NMR characterization of AER and AERMT. FIG. 2 is a graph of AER and AERMT¹H NMR, AER and AERMT in FIGS. 3 and 4, respectively¹³C NMR spectrum, it can be clearly observed from the spectrum that the peaks in the NMR spectrum correspond to the protons and C atoms of the product one by one, and the results can fully prove that AER and AERMT are successfully synthesized.

Infrared characterization of APU-1

FIG. 5 represents the reaction of a chain extended isocyanate-terminated compound (PCL/HMDI) with an anthracene-based side chain-containing hydroxyl-terminated compound (AERMT) and 1, 4-Butanediol (BD) to produce an adhesive (APU-1) of linear polyurethane structure containing anthracene side groups and a polycaprolactone crystalline segment. FIG. 5a is a graph representing the spectrum of PCL/HMDI, and FIG. 5b is a graph representing the spectrum of APU-1; at 2260cm^-1The left and right absorption peaks represent-NCO, 3300cm^-1The left and right absorption peaks represent-N-H, 2260cm in the spectrum of APU^-1The absorption peaks at the left and right disappeared, and 3300cm^-1The relative height of the left and right absorption peaks becomes larger, which proves that-NCO is consumed by the reaction of-OH and-NCO, and-N-H is generated.

XRD characterization of APU-1

FIG. 6 depicts the phase structure of APU-1 by XRD, showing a typical amorphous broad band ranging from 10 to 30 with crystalline peaks at 21 and 23 corresponding to the crystalline segment of polycaprolactone diol (PCL-2 OH). This indicates the presence of both crystalline and amorphous phases in the APU-1 system.

Characterization of the operability of APU-1

Characterization of the molecular weight and molecular weight distribution of the APU-1 product by the GPC test of FIG. 7 yields a number average molecular weight (M)_n) A weight average molecular weight (M) of 16704_w) 41382, molecular weight distribution (PDI) of 2.48; FIG. 8 represents the crystallization rate of APU-1 at room temperature by DSC cooling-warming scan, by formula

The crystallinity, Δ H, after 20min incubation at room temperature was calculated_mRepresents the fusion enthalpy, Δ H, in FIG. 8_cThe difference obtained by subtracting the values of the enthalpy of crystallization represented in FIG. 8 can be considered as the value of enthalpy of crystallization, Δ H, during the incubation at room temperature_100％Representing the theoretical enthalpy of crystallization of PCL, which is known from a review of the literature to be equal to 135J/g, and a crystallinity of 3.3% after 20min incubation at room temperature is obtained by calculation, the product having sufficient operability since the photocuring process is completed within 5 min; as shown in FIG. 9, the viscosity-temperature curve of APU-1 was measured by rheometer, resulting in a melt viscosity of 152930mPa.s at room temperature.

6. Cured UV-visible absorption spectrum tracking

To obtain the best curing time for APU-1 and to confirm complete curing, uv-vis absorption spectroscopy was used to follow the crosslinking curing process of step 5 in example 1. Samples were irradiated with UV light (40W) at 365nm for different periods of time to obtain different degrees of cure, as shown in FIG. 10. As can be seen from the figure, the absorption peaks of 4 representatives of the anthracene group are gradually reduced along with the prolonging of the illumination time, and the absorption value is not changed after 5 min. By the formula:

the degree of curing reaction, A, was calculated₀Representing a wavelength of 390nm before the illuminationAbsorption number of A₁The absorption value at the wavelength of 390nm after the illumination is shown, and the curing rate reaches 89% through calculation.

Crystallinity and glass transition temperature before and after solidification of APU-1

DSC can be used to monitor the changes of crystallinity and glass transition temperature before and after solidification of APU-1, as shown in FIG. 11 and FIG. 12, wherein a and b in FIG. 11 are the crystalline melting curves before and after solidification in example 1, respectively, and a and b in FIG. 12 are the glass transition temperature curves before and after solidification in example 1, respectively. By the formula:

wherein Δ H_mRepresents the melting enthalpy values, Δ H, in the curves 11a and 11b_100％Representing the theoretical enthalpy of crystallization of PCL, which is known from a review of the literature to be equal to 135J/g, the crystallinity before curing is calculated to be 30.3% and the crystallinity after curing to be 20.8%, and the crystalline segments after curing are degraded due to the movement of the segments being restricted by the crosslinked structure. Curve 12a does not show a glass transition temperature because the glass transition temperature before curing is too low to exceed the DSC measurement range, and curve 12b shows a glass transition temperature after curing of-47.9 ℃.

Characterization of bonding strength of APU-1 after curing and photolysis

Coating the APU-1 melt on a quartz substrate, covering the quartz substrate with another quartz substrate, and fully infiltrating the adhesive into the adhesive joint by using 20KPa constant pressure, wherein the adhesive area is 75mm². Subsequently, it was cured by irradiation with 365nm ultraviolet light (20W) for 5 minutes and allowed to stand at room temperature for 2 hours to sufficiently crystallize. The bonding strength is tested by using the lap shear strength test method, and the bonding strength can reach 3.8MPa, as shown in figure 13a, and is superior to other currently reported photo-reversible adhesives.

Using the lap joint sample prepared in the same manner as above, the bonding strength was still tested by the lap shear strength test method under irradiation of uv light (8W) at 254nm for 1h, and it was found that the bonding strength was significantly reduced to 2.1MPa, as shown in fig. 13b, but the bonded joint still had a certain bonding strength due to the existence of the crystalline structure, the photolyzed adhesive was soaked in acetone for 10 minutes, and the linear polyurethane polymer recovered after photolysis was dissolved in acetone and no more polymer remained on the substrate.

Example 2

The adhesive has the same structure as example 1.

The preparation method comprises the following steps:

1) preparation of anthracene-containing epoxidation product: 1mol of 9-Anthracene Methanol (AM) raw material is dissolved in 20mol of nonpolar solvent toluene, 5mol of epichlorohydrin is added, the temperature is kept at 60 ℃ in a water bath, and then 2mol of sodium hydroxide and 0.01mol of tetramethyl ammonium bromide (TMAB) are added. Stirring and reacting for 6h under the condition of heat preservation, and obtaining an anthracene-based epoxy product, namely 9-anthracene methanol epoxide (AER), through centrifugation, toluene extraction, rotary evaporation and vacuum drying;

2) preparation of double-terminal hydroxyl compound containing anthracene-based side chain: mixing 0.5mol of 9-anthracene methanol epoxide prepared in the step 1) with 0.5mol of mercaptoethanol, dissolving in 10mol of toluene, adding DMP-30 accelerator in an amount of 0.5% by mass fraction, uniformly stirring, reacting at room temperature (20 ℃) for 3 hours, and performing rotary evaporation and vacuum drying to obtain an anthracene group-containing epoxidation product (AERMT);

3) preparation of chain-extended, double-ended isocyanate-based compounds: 0.04mol of 4, 4-dicyclohexylmethane diisocyanate (HMDI) and 0.02mol of bis-hydroxy-terminated polycaprolactone (M)_w2000), namely polycaprolactone diol (PCL-2OH), is dissolved in 0.6mol of methyl isobutyl ketone solvent, dibutyltin dilaurate (DBTDL) catalyst is added in 0.5% by mass, after uniform stirring, reaction is carried out at 70 ℃ for 3h, and through rotary evaporation and vacuum drying, a chain-extended isocyanate-terminated compound (PCL/HMDI) is obtained;

4) the preparation of the linear polyurethane structure compound containing anthracene side group and polycaprolactone crystal chain segment comprises the following steps: 0.02mol of PCL/HMDI, 0.016mol of AERMT and 0.004mol of 1, 4-Butanediol (BD) are dissolved in 0.6mol of methyl isobutyl ketone solvent, the molar ratio of isocyanate groups to hydroxyl groups is 1:1, dibutyltin dilaurate (DBTDL) catalyst is added according to 0.5 mass percent, and the mixture is uniformly stirred and reacts for 3 hours at 70 ℃ to obtain the high-strength light reversible adhesive (APU-2).

5) And (3) curing: preheating the adhesive prepared in the step 4) at 60 ℃ for 1min in advance to melt the adhesive, fixing two quartz glass substrates, applying rated pre-pressure (20KPa), and then transferring the melt to ultraviolet light (40W) with the wavelength of 405nm to irradiate for 5min to solidify the melt, so as to obtain the solidified high-strength light reversible adhesive (CL-APU-2) containing the anthracene group and the polycaprolactone crystalline chain segment.

The obtained cured adhesive is placed at room temperature (25 ℃) for 2 hours to be fully crystallized, and is subjected to a tensile shear test, the bonding strength of the cured adhesive to quartz glass is 3.1MPa, the cured adhesive is irradiated for 2 hours under 254nm ultraviolet light (8W), the strength after photodegradation is 1.7MPa, and the adhesive still has certain bonding strength due to the existence of a crystalline chain segment. The photolyzed adhesive was soaked in acetone for 10 minutes and the linear polyurethane polymer recovered after photolysis was dissolved in acetone and no more polymer remained on the substrate.

And (3) testing and characterizing:

infrared Spectrum characterization of AER and AERMT

FIG. 14 is an infrared spectrum of 9-Anthracenemethanol (AM), 9-Anthracenemethanol Epoxide (AER) and the double-terminal hydroxyl compound having an anthracenyl side chain (AERMT) in example 2, in which 14a is an infrared spectrum of AM at 3400cm^-1The nearby broad peak is attributed to the vibration of-OH, and after the reaction, the disappearance of the absorption can be observed, indicating that-OH is completely consumed in the reaction; 14b is the spectrum of AER at 913cm^-1The absorption at (a) represents the characteristic absorption of the epoxy group, indicating that the epoxidation reaction between epichlorohydrin and-OH groups has been successfully carried out. 14c is the spectrum of AERMT at 913cm^-1The absorption peak at (1) disappears, 3400cm^-1The re-appearance of a broad peak near the ring opening reaction due to-OH proves that the ring opening reaction of the epoxy group forms-OH.

NMR characterization of AER and AERMT

To further confirm the structure, we performed AER and AERMTAnd (5) NMR characterization. FIG. 15 is of AER and AERMT¹H NMR, AER and AERMT in FIGS. 16 and 17, respectively¹³C NMR spectrum, it can be clearly observed from the spectrum that the peaks in the NMR spectrum correspond to the protons and C atoms of the product one by one, and the results can fully prove that AER and AERMT are successfully synthesized.

Infrared characterization of APU-2

FIG. 18 represents the reaction of a chain extended terminal isocyanate-based compound (PCL/HMDI) with a terminal hydroxy compound containing an anthracenyl side chain (AERMT) and 1, 4-Butanediol (BD) to produce a compound of linear polyurethane structure (APU-2) containing anthracenyl side groups and a polycaprolactone crystalline segment. FIG. 18a is a graph representing the spectrum of PCL/HMDI, and FIG. 18b is a graph representing the spectrum of APU-2; at 2260cm^-1The left and right absorption peaks represent-NCO, 3300cm^-1The left and right absorption peaks represent-N-H, 2260cm in the spectrogram of APU-2^-1The absorption peaks at the left and right disappeared, and 3300cm^-1The relative height of the left and right absorption peaks becomes larger, which proves that-NCO is consumed by the reaction of-OH and-NCO, and-N-H is generated.

XRD characterization of APU-2

FIG. 19 depicts the phase structure of APU-2 by XRD, showing a typical amorphous broad band ranging from 10 to 30 with crystalline peaks at 21 and 23 corresponding to the crystalline segment of polycaprolactone diol (PCL-2 OH). This indicates the presence of both crystalline and amorphous phases in the APU-2 system.

Characterization of the operability of APU-2

Characterization of the molecular weight and molecular weight distribution of the APU-2 product by the GPC test of FIG. 20, yielding a number average molecular weight (M)_n) A weight average molecular weight (M) of 14598_w) 38902, molecular weight distribution (PDI) of 2.66; FIG. 21 characterizes the crystallization rate of APU-2 at room temperature by DSC ramp-up scan, by formula

The crystallinity, Δ H, after 20min incubation at room temperature was calculated_mRepresents the fusion enthalpy, Δ H, in FIG. 21_cThe difference between the two values representing the enthalpy of crystallization in FIG. 21 can be considered as the difference at room temperatureCrystallization enthalpy, Δ H, during lower temperature holding_100％Representing the theoretical enthalpy of crystallization of PCL, which is known from a review of the literature to be equal to 135J/g, and a crystallinity of 2.0% after 20min incubation at room temperature is obtained by calculation, the product having sufficient operability since the photocuring process is completed within 5 min; because APU-2 has more pendant groups relative to the product APU-1, the distance between molecular chains increases, which slows down the rate of crystallization under isothermal conditions and decreases the degree of crystallinity. As shown in fig. 22, the viscosity-temperature curve of APU-2 was tested by rheometer, resulting in a melt viscosity of 280520mpa.s at room temperature. Compared with APU-1, the viscosities of the two samples are significantly different at relative molecular weights close to the molecular weight distribution, probably because more aromatic side groups directly interact with stronger pi-pi.

6. Cured UV-visible absorption spectrum tracking

To obtain the best cure time for APU-2 and to confirm complete cure, the crosslinking cure process of step 5 in example 2 was followed using uv-vis absorption spectroscopy. Samples were irradiated with UV light (40W) at 405nm for different periods of time to obtain different degrees of cure, as shown in FIG. 23. As can be seen from the figure, the absorption peaks of 4 representatives of the anthracene group are gradually reduced along with the prolonging of the illumination time, and the absorption value is not changed after 5 min. By the formula:

the degree of curing reaction, A, was calculated₀Denotes the absorption value at a wavelength of 390nm before the light irradiation, A₁The absorption value at a wavelength of 390nm after the illumination is shown, and the curing rate is calculated to reach 75%. This is because the greater viscosity of sample APU-2 places some restriction on the segmental motion, resulting in a lower cure rate than APU-1.

Crystallinity and glass transition temperature before and after APU-2 solidification

DSC can be used to monitor the changes of crystallinity and glass transition temperature before and after solidification of APU-2, as shown in FIG. 24 and FIG. 25, wherein a and b in FIG. 24 are the crystalline melting curves before and after solidification in example 2, respectively, and a and b in FIG. 25 are the glass transition temperature curves before and after solidification in example 2, respectively. By the formula:

wherein Δ H_mRepresents the melting enthalpy values, Δ H, in curves 24a and 24b_100％Representing the theoretical enthalpy of crystallization of PCL, which is known from a review of the literature to be equal to 135J/g, the crystallinity before curing is calculated to be 24.6%, and the crystallinity after curing is calculated to be 18.9%, with the crystalline segments after curing being degraded due to the movement of the segments being restricted by the crosslinked structure. While, as stated above, APU-2, both before and after curing, should have a lower crystallinity than APU-1, as is normal. Curve 25a does not show a glass transition temperature, since the glass transition temperature before curing is too low to exceed the DSC measurement range, and curve 25b shows a glass transition temperature after curing of-54.5 ℃. Although the crosslink density of APU-2 is theoretically greater than that of APU-1, the glass transition temperature is lower than that of APU-1, which is also due to the lower crystallinity of sample APU-2 compared to APU-1.

Characterization of bonding strength of APU-2 after curing and photolysis

Coating the APU-2 molten mass on a quartz substrate, covering the quartz substrate with another quartz substrate, and fully infiltrating the adhesive into the adhesive joint by using 20KPa constant pressure, wherein the adhesive area is 75mm². Subsequently, it was cured by irradiation with 365nm ultraviolet light (20W) for 5 minutes and allowed to stand at room temperature for 2 hours to sufficiently crystallize. The bonding strength is tested by using a lap shear strength test method, and the bonding strength can reach 3.1MPa, as shown in figure 26a, and is superior to other currently reported photo-reversible adhesives. It can be seen from the data that the adhesive strength of the sample in example 2 is lower than that of example 1, because the adhesive strength of the sample is maintained by the cross-linked structure and the crystalline structure together, and the synergistic effect of the two acts as a high adhesive strength. Thus, for the crosslinked segmentThe ratio of crystalline segments is very important to control. Of these, the proportion of the sample in example 1 was clearly more suitable, while the sample in example 2 had a smaller content of crystalline segments and a slightly weaker effect on the adhesion enhancement.

Using the lap joint sample prepared in the same manner as above, irradiation for 1h under 254nm ultraviolet light (8W), the bond strength was still passed, the lap shear strength test method tested, and it was found that the bond strength was significantly reduced to 1.7MPa, as shown in fig. 26b, but the bonded joint still had a certain bond strength due to the presence of the crystalline structure, the photolyzed adhesive was soaked in acetone for 10 minutes, the linear polyurethane polymer recovered after photolysis was dissolved in acetone, and no more polymer remained on the substrate.

Example 3

The adhesive has the same structure as example 1.

The preparation method comprises the following steps:

1) preparation of anthracene-containing epoxidation product: dissolving 1mol of 9-Anthracene Methanol (AM) raw material in 30mol of nonpolar solvent toluene, adding 10mol of epichlorohydrin, keeping the temperature in a water bath at 70 ℃, and then adding 4mol of sodium hydroxide and 0.03mol of tetramethyl ammonium bromide (TMAB). Stirring and reacting for 6h under the condition of heat preservation, and obtaining an anthracene-based epoxy product, namely 9-anthracene methanol epoxide (AER), through centrifugation, toluene extraction, rotary evaporation and vacuum drying;

2) preparation of double-terminal hydroxyl compound containing anthracene-based side chain: mixing 0.5mol of the 9-anthracene methanol epoxide prepared in the step 1) with 0.55mol of mercaptoethanol, dissolving in 15mol of toluene, adding 1% of DMP-30 accelerator by mass fraction, uniformly stirring, reacting at room temperature (30 ℃) for 2 hours, and performing rotary evaporation and vacuum drying to obtain an anthracene group-containing epoxidation product (AERMT);

3) preparation of chain-extended, double-ended isocyanate-based compounds: 0.042mol of 4, 4-dicyclohexylmethane diisocyanate (HMDI) and 0.02mol of bis-hydroxy-terminated polycaprolactone (M)_w2000), namely polycaprolactone diol (PCL-2OH), is dissolved in 0.8mol of methyl isobutyl ketone solvent, dibutyltin dilaurate (DBTDL) catalyst is added in a mass fraction of 1%, and stirring is carried outAfter being uniformly mixed, the mixture reacts for 2 hours at 80 ℃, and the chain-extended isocyanate-terminated compound (PCL/HMDI) is obtained through rotary evaporation and vacuum drying;

4) the preparation of the linear polyurethane structure compound containing anthracene side group and polycaprolactone crystal chain segment comprises the following steps: 0.022mol of PCL/HMDI, 0.004mol of AERMT and 0.016mol of 1, 4-Butanediol (BD) are dissolved in 0.8mol of methyl isobutyl ketone solvent, the molar ratio of isocyanate groups to hydroxyl groups is 1.1:1, dibutyltin dilaurate (DBTDL) catalyst is added according to 1% of mass fraction, and the mixture is uniformly stirred and reacted for 2h at 80 ℃ to obtain the high-strength light reversible adhesive (APU-3).

5) And (3) curing: preheating the adhesive prepared in the step 4) at 60 ℃ for 1min in advance to melt the adhesive, fixing two quartz glass substrates, applying a rated pre-pressure (20KPa), and then transferring the melt to ultraviolet light (40W) with the wavelength of 405nm to irradiate for 10min to solidify the melt, so as to obtain the solidified high-strength light reversible adhesive (CL-APU-3) containing the anthracene group and the polycaprolactone crystal chain segment.

The cured adhesive was allowed to stand at room temperature (25 ℃) for 2 hours to sufficiently crystallize, and a tensile shear test was carried out, whereby the adhesive strength to quartz glass was measured to be 3.0MPa (FIG. 31a), the adhesive was irradiated with 254nm ultraviolet light (8W) for 2 hours, the strength after photodegradation was measured to be 2.8MPa (FIG. 31b), and the adhesive still had a certain adhesive strength because the crystalline segment was still present. The photolyzed adhesive was soaked in acetone for 30 minutes and the linear polyurethane polymer recovered after photolysis was dissolved in acetone and no more polymer remained on the substrate.

And (3) testing and characterizing:

infrared Spectrum characterization of AER and AERMT

FIG. 27 is an infrared spectrum of 9-Anthracenemethanol (AM), 9-Anthracenemethanol Epoxide (AER) and the double-terminal hydroxyl compound having an anthracenyl side chain (AERMT) in example 3, in which 27a is an infrared spectrum of AM at 3400cm^-1The nearby broad peak is attributed to the vibration of-OH, and after the reaction, the disappearance of the absorption can be observed, indicating that-OH is completely consumed in the reaction; 27b is the spectrum of AER at 913cm^-1The absorption at (A) represents the characteristic absorption of an epoxy groupAnd finally, indicating that the epoxidation reaction between the epichlorohydrin and the-OH group is successfully carried out. 27c is the spectrum of AERMT at 913cm^-1The absorption peak at (1) disappears, 3400cm^-1The reappearance of a broad peak near the ring opening reaction due to-OH proves that the ring opening reaction of the epoxy group forms-OH.

NMR characterization of AER and AERMT

To further confirm the structure, we performed NMR characterization of AER and AERMT. FIG. 28 is of AER and AERMT¹H NMR, AER and AERMT in FIGS. 29 and 30, respectively¹³C NMR spectrum, it can be clearly observed from the spectrum that the peaks in the NMR spectrum correspond to the protons and C atoms of the product one by one, and the results can fully prove that AER and AERMT are successfully synthesized.

Infrared characterization of APU-3

Fig. 31 represents the reaction of a chain extended isocyanate-terminated compound (PCL/HMDI) with a hydroxyl-terminated compound containing an anthracenyl side chain (AERMT) and 1, 4-Butanediol (BD) to produce a compound of linear polyurethane structure (APU-3) containing an anthracenyl side group and a polycaprolactone crystalline segment. FIG. 31a is a graph representing the spectrum of PCL/HMDI, and FIG. 31b is a graph representing the spectrum of APU-3; at 2260cm^-1The absorption peaks at the left and right represent-NCO, 3300cm^-1The left and right absorption peaks represent-N-H, 2260cm in the spectrum of APU-3^-1The absorption peaks on the left and right disappeared, and 3300cm^-1The relative height of the left and right absorption peaks becomes larger, which proves that-NCO is consumed by the reaction of-OH and-NCO, and-N-H is generated.

XRD characterization of APU-3

FIG. 32 depicts the phase structure of APU-3 by XRD, ranging from 10 to 30 showing a typical amorphous broad band with crystalline peaks at 21 and 23 corresponding to the crystalline segment of polycaprolactone diol (PCL-2 OH). This indicates the presence of both crystalline and amorphous phases in the APU-3 system.

Characterization of the operability of APU-3

Characterization of the molecular weight and molecular weight distribution of the APU-3 product by the GPC test of FIG. 33, yielding a number average molecular weight (M)_n) A weight average molecular weight (M) of 11957_w) 25609, molecular weight distribution (PDI) of 2.14; FIG. 34 shows a schematic view of a circuitDSC cooling-heating scanning represents the crystallization rate of APU-3 at room temperature, and the formula is shown

The crystallinity, Δ H, after 20min incubation at room temperature was calculated_mRepresents the fusion enthalpy, Δ H, in FIG. 34_cThe difference obtained by subtracting the crystallization enthalpy values represented in FIG. 34 can be considered as the crystallization enthalpy value, Δ H, during the incubation at room temperature_100％Representing the theoretical enthalpy of crystallization of PCL, which is equal to 135J/g, calculated to give a crystallinity of 14.3% after 20min incubation at room temperature. The faster crystallization rate is due to the lower content of aromatic side groups and the denser arrangement of molecular segments. This makes sample APU-3 less operable than APU-1 and APU-2. As shown in FIG. 35, the viscosity-temperature curve of APU-3 was determined by rheometer measurements to obtain a melt viscosity of 338950mPa.s at room temperature, with APU-3 having a lower relative molecular weight but a higher viscosity than APU-1 and APU-2 due to its higher crystallinity and crystallization rate. From the results of the three groups of APU samples, too much and too little aromatic side groups adversely affect crystallinity and viscosity for operability.

6. Cured UV-visible absorption spectrum tracking

To obtain the best cure time for APU-3 and to confirm complete cure, the crosslinking cure process of step 5 in example 3 was followed using uv-vis absorption spectroscopy. Samples were irradiated with UV light (40W) at 365nm for different periods of time to obtain different degrees of cure, as shown in FIG. 36. As can be seen from the figure, the absorption peaks of 4 representatives of the anthracene group are gradually reduced along with the prolonging of the illumination time, and the absorption value is not changed after 10 min. By the formula:

the degree of curing reaction, A, was calculated₀Denotes the absorption value at a wavelength of 390nm before the light irradiation, A₁Indicating illuminationThe absorption value at the wavelength of 390nm is calculated to obtain that the curing rate reaches 70 percent. This is also due to the effect of the higher viscosity, as discussed above.

Crystallinity and glass transition temperature before and after APU-3 solidification

DSC can be used to monitor the changes of crystallinity and glass transition temperature before and after solidification of APU-3, as shown in FIG. 37 and FIG. 38, wherein a and b in FIG. 37 are the crystalline melting curves before and after solidification in example 3, respectively, and a and b in FIG. 38 are the glass transition temperature curves before and after solidification in example 3, respectively. By the formula:

wherein Δ H_mRepresents the melting enthalpy values, Δ H, in the curves 37a and 37b_100％Representing the theoretical enthalpy of crystallization of PCL, which is known from a review of the literature to be equal to 135J/g, the crystallinity before curing is calculated to be 30.3% and the crystallinity after curing to be 20.8%, and the crystalline segments after curing are degraded due to the movement of the segments being restricted by the crosslinked structure. Curve 38a does not show a glass transition temperature because the glass transition temperature before curing is too low to exceed the DSC measurement range, and curve 38b shows a glass transition temperature after curing of-35.9 ℃. Although the crosslinking density of APU-1 and APU-2 is theoretically greater than that of APU-3, the glass transition temperature is lower than that of APU-3, and the phenomenon is also caused by the higher crystallinity of the sample APU-3.

Characterization of bonding strength of APU-3 after curing and photolysis

Coating the APU-3 melt on a quartz substrate, covering the quartz substrate with another quartz substrate, and fully infiltrating the adhesive into the adhesive joint by using 20KPa constant pressure, wherein the adhesive area is 75mm². Subsequently, it was cured by irradiation with 365nm ultraviolet light (20W) for 5 minutes and allowed to stand at room temperature for 2 hours to sufficiently crystallize. The bonding strength is tested by using the lap shear strength test method, the bonding strength can reach 3.0MPa, and as shown in figure 39a, the bonding strength is superior to other optical fibers reported at presentAnd (4) inverse adhesive. It can be seen from the data that the adhesive strength of the sample in example 3 is also lower than that of example 1. This is because the sample in example 3 has less cross-linked structure, which is the same as example 2, and it also indicates that the adhesive strength of the sample is maintained by the cross-linked structure and the crystalline structure, and the synergistic effect of the two has the effect of high adhesive strength, and it is very important to adjust the ratio between the two.

Using the lap joint samples prepared in the same manner as above, the bond strength was tested by the lap shear strength test method under irradiation of 254nm uv light (8W) for 1h, and was found to drop significantly to 2.8 MPa. We found that the intensity drop was minimal for example 3 relative to examples 1 and 2. This is because the APU-3 sample has the lowest cross-linking density and the highest crystallinity, and correspondingly, the shear strength decreases the least after the decrosslinking reaction, as compared to the APU-1 and APU-2 samples. As shown in fig. 39b, since the crystal structure still existed, the bonded joint still had a certain bonding strength, and the photolyzed adhesive was immersed in acetone for 30 minutes, and the linear polyurethane polymer recovered after photolysis was dissolved in acetone, and no polymer remained on the substrate.

Claims (10)

1.A high-strength photo-reversible adhesive characterized by:

the adhesive comprises the following structure:

0< q < 8; 0< p < 7; 0< n < 8; 0< m < 6; and p, q, n, m are integers;

wherein, the first and the second end of the pipe are connected with each other,

a is

B is as follows:

a is an integer between 19 and 40;

d is as follows:

b is an integer of 4-6;

r is

2. The high intensity photo-reversible adhesive of claim 1 wherein:

the adhesive is cured under the irradiation of ultraviolet light with the wavelength of 350-405 nm;

and (3) carrying out de-crosslinking under the irradiation of ultraviolet light with the wavelength of less than 300 nm.

3.A method of preparing an adhesive as claimed in claim 1 or 2, characterized in that it comprises:

dissolving an anthracene-based compound in a solvent A, then adding an epoxy compound, alkali and a phase transfer catalyst, and stirring for reaction to obtain an anthracene-based epoxidation product;

step (2), dissolving the epoxidation product containing the anthracene group obtained in the step (1) in a solvent B, adding a thiol-terminated compound and an accelerator, and stirring for reaction to obtain a hydroxyl-terminated compound containing an anthracene group side chain;

dissolving the isocyanate-terminated compound and the hydroxyl-terminated polycaprolactone in a solvent C, adding an organic tin catalyst, and stirring for reaction to generate a chain-extended isocyanate-terminated compound;

and (4) dissolving the chain-extended double-ended isocyanate compound, the double-ended hydroxyl compound containing the anthryl side chain and the double-ended hydroxyl compound not containing the anthryl side chain in a solvent D, adding an organic tin catalyst, and stirring for reaction to obtain the high-strength photo-reversible adhesive.

4. The method of claim 3, wherein:

in the step (1), the step (c),

the anthracene-based compound is selected from 9-anthracene methanol and/or 1- (9-anthracene-based) ethanol; and/or the presence of a gas in the gas,

the epoxy compound is selected from epoxy halogen compounds; and/or the presence of a gas in the gas,

the alkali is selected from sodium hydroxide and/or potassium hydroxide; and/or the presence of a gas in the gas,

the phase transfer catalyst is selected from tetramethylamine halogen compounds; and/or the presence of a gas in the atmosphere,

the solvent A is a non-polar solvent; and/or the presence of a gas in the gas,

the molar ratio of the anthracene-based compound to the epoxy compound to the base to the phase transfer catalyst is 1: (5-10): (2-4): (0.01-0.03);

the molar ratio of the anthracene-based compound to the solvent A is 1: 20-1: 30;

the stirring reaction temperature is 60-70 ℃, and the stirring reaction time is 3-6 h.

5. The method of claim 3, wherein:

in the step (2),

the solvent B is a non-polar solvent; and/or the presence of a gas in the gas,

the accelerator is selected from tertiary amine compounds; and/or the presence of a gas in the gas,

the thiol-terminated compound is 2-mercaptoethanol;

the molar ratio of the anthracene-based epoxidation product to the solvent B is 1: 20-1: 30;

the molar ratio of the anthracene-group-containing epoxidation product to the mercapto-terminated alcohol compound is 1: 1-1: 1.1;

the amount of the accelerant is 0.5 to 1 weight percent of the total weight of the anthracene-based epoxidation product and the end mercapto alcohol compound;

the stirring reaction temperature is 20-30 ℃, and the stirring reaction time is 2-3 h.

6. The method of claim 3, wherein:

in the step (3), the step (c),

the double-end isocyanate group compound is selected from one of 4, 4-diphenylmethane diisocyanate, 4, 4-dicyclohexylmethane diisocyanate and hexamethylene diisocyanate; and/or the presence of a gas in the gas,

the solvent C is a polar solvent; and/or the presence of a gas in the gas,

the organic tin catalyst is dibutyltin dilaurate; and/or the presence of a gas in the gas,

the molar ratio of the double-end hydroxyl polycaprolactone to the solvent C is 1: 30-1: 40;

the dosage of the catalyst is 0.5-1 wt% of the total weight of the double-end isocyanate-based compound and the double-end hydroxyl polycaprolactone;

the molar ratio of the double-end isocyanate group compound to the double-end hydroxyl polycaprolactone is 2: 1-2.1: 1;

the stirring reaction temperature is 70-80 ℃, and the stirring reaction time is 2-3 h.

7. The method of claim 3, wherein:

in the step (4), the step (c),

the double-end hydroxyl compound without the anthryl side chain is selected from one of 1, 4-butanediol, 1, 5-pentanediol and 1, 6-hexanediol; and/or the presence of a gas in the gas,

the solvent D is a polar solvent; and/or the presence of a gas in the gas,

the molar ratio of the isocyanate group to the hydroxyl group is 1: 1-1.1: 1;

the molar ratio of the double-terminal hydroxyl compound containing the anthryl side chain to the double-terminal hydroxyl compound not containing the anthryl side chain is 1: (0.25 to 4);

the organic tin catalyst is dibutyltin dilaurate;

the dosage of the catalyst is 0.5 to 1 weight percent of the total weight of the chain-extended double-end isocyanate compound, the double-end hydroxyl compound containing the anthryl side chain and the double-end hydroxyl compound not containing the anthryl side chain;

the molar ratio of the chain-extended double-end isocyanate group compound to the solvent D is 1: 30-1: 40;

the stirring reaction temperature is 70-80 ℃, and the stirring reaction time is 2-3 h.

8. The method according to any one of claims 3 to 7, wherein:

centrifuging, extracting, rotary evaporating and drying the anthracene-based-containing epoxidation product obtained in the step (1); wherein the extraction solvent is at least one selected from toluene, methyl isobutyl ketone and ethyl acetate;

and (3) removing the solvent from the product obtained in the steps (2), (3) and (4) in vacuum heating equipment, wherein the heating temperature is 90-100 ℃, and the heating time is 2-3 h.

9. A high-strength photo-reversible adhesive prepared by the method of any one of claims 3 to 8.

10. Use of an adhesive according to any one of claims 1, 2 or 9 in a light-transmitting substrate.

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