CN110317325B - Linear comb-shaped polylactic acid and preparation method thereof - Google Patents
Linear comb-shaped polylactic acid and preparation method thereof Download PDFInfo
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- CN110317325B CN110317325B CN201810265695.4A CN201810265695A CN110317325B CN 110317325 B CN110317325 B CN 110317325B CN 201810265695 A CN201810265695 A CN 201810265695A CN 110317325 B CN110317325 B CN 110317325B
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Abstract
The invention relates to a linear comb-shaped polylactic acid, the molecular structure of which is shown as the formula (I). Wherein R is1Selected from hydrogen or C1‑C6Alkyl groups of (a); r2Is selected from C2‑C5An alkylene group of (a); x, y, z, m and n are positive integers; the number average molecular weight of the linear comb-shaped polylactic acid is (0.1-100) multiplied by 104. The invention also relates to a preparation method of the linear comb-shaped polylactic acid, and the linear comb-shaped polylactic acid prepared by adopting the method of combining anion polymerization and click chemistry has the characteristics of high molecular weight, narrow distribution and high branched structure; the whole synthesis process has relatively few steps, high reaction efficiency and controllable branching degree, and the prepared linear comb-shaped polylactic acid has excellent physical properties and processing properties.
Description
Technical Field
The invention belongs to the technical field of high polymer materials, and particularly relates to linear comb-shaped polylactic acid and a preparation method thereof.
Background
Polylactic acid (PLA) is a "green polymer" material derived from renewable resources and that can be completely degraded into carbon dioxide and water. The composite material has no toxicity, no irritation, excellent biocompatibility, biological absorbability, complete biodegradability and excellent physical and mechanical properties, so that the composite material is more and more widely concerned. Polylactic acid can be subjected to various forming processing like common polymers, and various films, sheets and fibers prepared from the polylactic acid are subjected to secondary processing such as thermoforming, spinning and the like, and are increasingly widely applied to the fields of spinning, packaging, agriculture, medical treatment and health, daily necessities and the like. However, the low melt strength, high brittleness, insufficient toughness and low elongation at break of the current commercial polylactic acid become key technical problems which hinder the development and application of the polylactic acid.
Therefore, the problem is that the linear comb-shaped polylactic acid with better mechanical property and processability needs to be researched and developed urgently.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a linear comb-shaped polylactic acid and a preparation method thereof, aiming at the defects of the prior art. The preparation method comprises the steps of utilizing anion active polymerization to prepare Polyisoprene (PI) with controllable molecular weight and narrow distribution, quantitatively converting double bonds of side chains in the polyisoprene into hydroxyl groups through click reaction of sulfydryl-double bonds to generate linear polyisoprene (PI-OH) with hydroxyl groups on side groups, using the PI-OH as a macromolecular initiator to initiate lactide ring opening, and preparing linear comb-shaped polylactic acid with high molecular weight, narrow distribution, high branching degree and controllable branching degree. The synthesis steps in the whole process are relatively few, the reaction efficiency is high, the reaction process is controllable, and the prepared linear comb-shaped polylactic acid has excellent physical properties and processability.
Therefore, the invention provides a linear comb-shaped polylactic acid, the molecular structure of which is shown in formula (I):
wherein R is1Selected from hydrogen or C1-C6Alkyl of (a), preferably hydrogen, methyl, ethyl or propyl, more preferably methyl; r2Is selected from C2-C5Alkylene of (2), preferably ethylene or propylene, more preferablyAn ethylene group; x, y, z, m and n are positive integers.
According to the invention, the linear comb-shaped polylactic acid has a number average molecular weight of (0.1-100). times.104Preferably (1-50). times.104。
According to the invention, the linear comb polylactic acid has a molecular weight distribution index (PDI) of 1.05 to 1.4, preferably 1.05 to 1.2.
The second aspect of the present invention provides a method for preparing the linear comb-shaped polylactic acid according to the first aspect of the present invention, which comprises the following steps:
s1, under the action of the initiator A, carrying out anionic polymerization on an isoprene monomer to prepare polyisoprene;
s2, under the protection of inert gas, enabling polyisoprene and mercaptoalkyl alcohol to perform click reaction under the action of an initiator B to prepare linear hydroxylated polyisoprene;
s3, under the protection of inert gas, carrying out polymerization reaction on linear hydroxylated polyisoprene and lactide monomer under the action of a catalyst to prepare linear comb-shaped polylactic acid;
wherein the linear hydroxylated polyisoprene has a hydroxyl number of 3 to 260, preferably 10 to 180, more preferably 19 to 100; preferably, the linear hydroxylated polyisoprene has a number average molecular weight of (0.05-3.5). times.104Preferably (0.1-3). times.104More preferably (0.2-1.5). times.104。
According to the method, in the step S1, the reaction temperature of the polymerization reaction is 0-50 ℃, and the reaction time is 0.5-12 h; the molar ratio of the initiator A to the isoprene is (2 x 10)-3-0.1):1。
According to the method of the invention, the initiator A is a compound shown as a formula II,
R3li (formula II)
In the formula (II), R3Is selected from C1-C6Alkyl of (C)3-C12Cycloalkyl of, C6-C12Aryl or C of7-C14An aralkyl group of (2).
According to some embodiments of the invention, the initiator A is selected from at least one of ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, phenyllithium, 2-naphthyllithium, 4-butylphenyl lithium, 4-methylphenyllithium, cyclohexyllithium and 4-butylcyclohexyllithium.
According to the method of the invention, the polyisoprene has a number average molecular weight of (0.05-3). times.104The content of the double bond of the side chain is 35 to 85 percent.
According to the method of the present invention, in step S1, the polymerization reaction is carried out in a solvent of n-hexane and/or tetrahydrofuran; when the polymerization reaction is carried out in a mixed solvent of n-hexane and tetrahydrofuran, the volume ratio of tetrahydrofuran to n-hexane in the mixed solvent is 1:30-30: 1.
According to the method, in step S2, the click reaction temperature is 60-70 ℃, and the reaction time is 12-24 h.
According to the method of the present invention, the initiator B is a thermal decomposition type radical initiator, preferably the initiator B is selected from at least one of peroxide type initiators and azobisnitrile type compound initiators, more preferably at least one selected from diacyl peroxide, peroxydicarbonate, peroxycarboxylic ester, alkyl peroxide and azobisnitrile type compounds, and most preferably at least one selected from dibenzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, di-o-methylbenzoyl peroxide, tert-butyl peroxybenzoate, dicumyl peroxide, azobisisobutyronitrile and azobisisoheptonitrile.
According to the process of the invention, in step S2, the molar ratio of the polyisoprene to the mercaptoalkyl alcohol is (0.1-60):1, preferably (0.2-40):1, more preferably (0.5-30): 1; the molar ratio of the initiator B to the polyisoprene is (0.1-0.8):1, preferably (0.2-0.5): 1.
According to the process of the present invention, in step S3, the molar ratio of the lactide monomer to the hydroxyl groups in the linear hydroxylated polyisoprene ranges from 5 to 800, preferably from 10 to 600.
According to the process of the present invention, the molar ratio of lactide monomer to catalyst is 300-.
According to the method of the invention, in step S3, the catalyst is selected from at least one of tin powder, inorganic salts of tin, organic salts of tin, oxides of antimony, organic acid rare earth compounds and iron compounds; preferably, the catalyst is at least one selected from the group consisting of tin powder, stannous chloride, stannous octoate, stannous benzoate and antimony trioxide.
According to the method of the present invention, the lactide monomer is selected from one or more of L-lactide, D-lactide, DL-lactide.
According to the method of the present invention, in step S3, the reaction temperature of the polymerization reaction is 110-140 ℃, and the reaction time is 1-6 h.
Detailed Description
In order that the present invention may be more readily understood, the following detailed description of the invention is given by way of example only, and is not intended to limit the scope of the invention.
In view of the technical problems of low melt strength, high brittleness, insufficient toughness and low elongation at break of polylactic acid in the prior art, the inventor of the invention discovers that polyisoprene with controllable molecular weight and narrow distribution is prepared by utilizing anion active polymerization, double bonds of side chains in the polyisoprene are quantitatively converted into hydroxyl groups through the click reaction of mercapto-double bonds to generate polyisoprene (PI-OH) with hydroxyl groups on the side groups, and the PI-OH is used as a macromolecular initiator to initiate lactide to open rings to prepare linear pectinate polylactic acid with controllable high molecular weight, narrow distribution, high branching degree and controllable branching degree. The whole synthesis process has relatively few steps, high reaction efficiency and controllable reaction process, and the prepared linear comb-shaped polylactic acid has excellent physical properties and processability. The present invention has been made based on the above findings.
Therefore, the linear comb-shaped polylactic acid according to the first aspect of the present invention has a molecular structure represented by formula (I):
wherein R is1Selected from hydrogen or C1-C6Alkyl of (a), preferably hydrogen, methyl, ethyl or propyl, more preferably methyl; r2Is selected from C2-C5Alkylene of (a), preferably ethylene or propylene, more preferably ethylene; x, y, z, m and n are positive integers.
The linear comb-shaped polylactic acid has a number average molecular weight of 0.1-100 x 104Preferably (1-50). times.104。
The linear comb-shaped polylactic acid has a molecular weight distribution index (PDI) of 1.05 to 1.4, preferably 1.05 to 1.2.
The second aspect of the present invention relates to a method for preparing linear comb-shaped polylactic acid according to the first aspect of the present invention, comprising the steps of:
s1, under the action of the initiator A, carrying out anionic polymerization on an isoprene monomer to prepare polyisoprene;
s2, under the protection of inert gas, enabling polyisoprene and mercaptoalkyl alcohol to perform click reaction under the action of an initiator B to prepare linear hydroxylated polyisoprene;
s3, under the protection of inert gas, carrying out polymerization reaction on linear hydroxylated polyisoprene and lactide monomer under the action of a catalyst to prepare linear comb-shaped polylactic acid;
wherein the linear hydroxylated polyisoprene has a hydroxyl number of 3 to 260, preferably 10 to 180, more preferably 19 to 100; preferably, the linear hydroxylated polyisoprene has a number average molecular weight of (0.05-3.5). times.104Preferably (0.1-3). times.104More preferably (0.2-1.5). times.104。
In the preparation method of the linear comb-shaped polylactic acid, the hydroxylation degree of the linear hydroxylated polyisoprene is 3-50%, preferably 5-35%.
In the preparation method of the linear comb-shaped polylactic acid, in step S1, the reaction temperature of the polymerization reaction is 0-50 ℃, and the reaction time is 0.5-12 h; the molar ratio of the initiator A to the isoprene is (2 x 10)-3-0.1):1。
In the preparation method of the linear comb-shaped polylactic acid, the initiator A is a compound shown in a formula II,
R3li (formula II)
In the formula (II), R3Is selected from C1-C6Alkyl of (C)3-C12Cycloalkyl of, C6-C12Aryl or C of7-C14An aralkyl group of (2).
In some preferred embodiments of the present invention, the initiator A is selected from at least one of ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, phenyllithium, 2-naphthyllithium, 4-butylphenyl lithium, 4-methylphenyllithium, cyclohexyllithium, and 4-butylcyclohexyllithium.
In the above preparation method of the linear comb-shaped polylactic acid, in step S1, the polymerization reaction is performed in a solvent of n-hexane and/or tetrahydrofuran, and when the polymerization reaction is performed in a mixed solvent of n-hexane and tetrahydrofuran, the volume ratio of tetrahydrofuran to n-hexane in the mixed solvent is 1:30-30: 1.
In the preparation method of the linear comb-shaped polylactic acid, the number average molecular weight of the polyisoprene is (0.05-3). times.104The content of the double bond of the side chain is 35 to 85 percent.
In the preparation method of the linear comb-shaped polylactic acid, in step S2, the reaction temperature of the click reaction is 60-70 ℃, and the reaction time is 12-24 h.
In some embodiments of the present invention, the initiator B is a thermal decomposition type radical initiator, preferably the initiator B is selected from at least one of peroxide type initiators and azobisnitrile type compound initiators, more preferably at least one selected from diacyl peroxide, peroxydicarbonate, peroxycarboxylate, alkyl peroxide and azobisnitrile type compounds, and most preferably at least one selected from dibenzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, di-o-methylbenzoyl peroxide, tert-butyl peroxybenzoate, dicumyl peroxide, azobisisobutyronitrile and azobisisoheptonitrile.
In the above method for producing linear comb-shaped polylactic acid, in step S2, the molar ratio of the polyisoprene to the mercaptoalkyl alcohol is (0.1-60):1, preferably (0.2-40):1, more preferably (0.5-30): 1; the molar ratio of the initiator B to the polyisoprene is (0.1-0.8):1, preferably (0.2-0.5): 1.
In some embodiments of the present invention, in step S2, the polyisoprene is reacted with the mercaptoalkyl alcohol and the initiator B dissolved in toluene to prepare a toluene solution with a concentration of 2 wt% to 8 wt%.
In the above method for preparing linear comb-shaped polylactic acid, in step S3, the molar ratio of the lactide monomer to the hydroxyl groups in the linear hydroxylated polyisoprene is 5 to 800, preferably 10 to 600.
In the above preparation method of linear comb-shaped polylactic acid, in step S3, the molar ratio of the lactide monomer to the catalyst is 300-.
In some embodiments of the present invention, in step S3, the required amount of solvent toluene and lactide monomer are sequentially added into a reactor with stirring to prepare a lactide solution with a molar concentration of 0.1-7M, the stirring is turned on, and linear hydroxylated polyisoprene and catalyst are sequentially added to react according to the designed molecular weight of the product.
In the above method for preparing linear comb-shaped polylactic acid, in step S3, the catalyst is at least one selected from the group consisting of tin powder, inorganic salts of tin, organic salts of tin, antimony oxides, organic acid rare earth compounds, and iron compounds; preferably, the catalyst is at least one selected from the group consisting of tin powder, stannous chloride, stannous octoate, stannous benzoate and antimony trioxide.
In the preparation method of the linear comb-shaped polylactic acid, the lactide monomer is selected from one or more of L-lactide, D-lactide and DL-lactide.
In the preparation method of the linear comb-shaped polylactic acid, the reaction temperature of the polymerization reaction is 110-140 ℃, and the reaction time is 1-6 h.
In the preparation method of the linear comb-shaped polylactic acid, the polymer solution obtained in the step S3 is subjected to post-treatment by a method commonly used in the field, and a product is dried, so that the linear comb-shaped polylactic acid is finally obtained.
In the above method for preparing linear comb-shaped polylactic acid, the inert gas is selected from nitrogen and/or argon.
The linear comb-shaped polylactic acid has the characteristics of high molecular weight, high branched structure and narrow distribution. The physical and mechanical properties of the polylactic acid are effectively improved due to high molecular weight and narrow distribution; meanwhile, the high-branched structure effectively improves the processing performance of the high-molecular-weight narrow-distribution polylactic acid. The preparation method has the advantages of simple process, stable and reliable preparation process, high reaction efficiency and controllable reaction process, and can adjust the proportion and the molecular weight of the main chain and the side chain according to the use requirement.
The characterization test method adopted by the invention is as follows:
(1) molecular weight and distribution thereof: using a Waters2690 liquid Gel Permeation Chromatography (GPC) instrument from Waters corporation, THF as a mobile phase, and 35 ℃ as a test temperature; measuring a calibration curve by adopting standard polystyrene;
(2) polyisoprene double bond content: by using1H-NMR method test;
(3) degree of hydroxylation and hydroxyl number of hydroxylated Polymer: by using1H-NMR method.
Examples
Example 1
(1) Preparation of Polyisoprene (PI)
Baking the dried polymerization bottle in high vacuum, pumping and replacing for 3 times by using argon, and injecting 150mL of mixed solvent of normal hexane and tetrahydrofuran and 12g of isoprene into the polymerization bottle in the atmosphere of argon, wherein the volume ratio of the tetrahydrofuran to the normal hexane is 1: 4; then n-butyllithium was injected in a molar ratio of n-butyllithium to isoprene of 1.15X 10-21, reacting for 12 hours at 0 ℃. And finally, injecting degassed methanol to terminate, pouring the degassed methanol into ethanol to precipitate to obtain white viscous substance poly-isopentene (PI), washing a polymerization product with ethanol for 3 times, and drying the product in vacuum for 4 hours. The number average molecular weight of the Polyisoprene (PI) product is 0.62 × 104The molecular weight distribution (PDI) was 1.03, 1, 2-polymerization 18.7 wt%, 3, 4-polymerization 66.1 wt%, 1, 4-polymerization 15.2 wt%.
(2) Preparation of Linear hydroxylated Polyisoprene (PI-OH)
6.7g of the Polyisoprene (PI) described above, as well as Azobisisobutyronitrile (AIBN) and mercaptoalkyl alcohol (RSH) were dissolved in 250mL of toluene in a reactor with a molar ratio of PI to AIBN [ PI]0/[AIBN]01:0.35, molar ratio of PI to RSH [ PI]0and/RSH is 30: 1. Then, the oxygen in the reactor is removed by freezing-air extraction-argon filling circulation for 3 times, and the reaction is carried out for 12 hours under the protection of nitrogen and under the oil bath at 60 ℃. Azodiisobutyronitrile (AIBN) is used as a free radical initiator, mercaptoalkyl alcohol directly reacts with double bonds on a side chain in polyisoprene, and hydroxyl is introduced into the side chain of the polyisoprene after the reaction is finished to obtain the product of linear hydroxylated polyisoprene (PI-OH). The test analysis showed that the linear hydroxylated polyisoprene (PI-OH) had a degree of hydroxylation of 21.73%, a hydroxyl number of 19.3, a number average molecular weight of 6500(GPC test) and a PDI of 1.06.
(3) Preparation of linear comb-shaped polylactic acid
The lactide monomer was dried at 60 ℃ under vacuum for 3h to remove water for use. Under inert atmosphere, 150mL solvent toluene and 32.4g L-lactide monomer are added into a reactor with stirring in sequence to prepare lactide solution with the molar concentration of 1.5M, the stirring is opened, and linear hydroxylated polyisoprene and catalyst are added in sequence according to the designed molecular weight of the product. Metering according to the molar ratio of lactide monomer to hydroxyl of 210, and adding 0.36g of the linear hydroxylated polyisoprene (PI-OH) prepared in the step (2); according to the molar ratio of the lactide monomer to the stannous octoate of 4000, 0.02g of catalyst stannous octoate is added. The reaction temperature is 130 ℃, and the polymerization reaction is controlled to be 4 hours. After the reaction is finished, the polymer solution is post-treated by a classical method, and a product is dried to finally obtain the linear comb-shaped polylactic acid. The number average molecular weight was 58.9X 10 by GPC4And PDI is 1.12.
Example 2
(1) Preparation of Polyisoprene (PI) and (2) preparation of Linear hydroxylated Polyisoprene (PI-OH) the same as in example 1.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as example 1, except that 0.626g of the linear hydroxylated polyisoprene (PI-OH) prepared in step (2) is added according to the molar ratio of the lactide monomer to the hydroxyl group of 120, and the product, linear comb polylactic acid, has a number average molecular weight of 33.7X 10 by GPC analysis4And PDI is 1.15.
Example 3
(1) Preparation of Polyisoprene (PI) and (2) preparation of Linear hydroxylated Polyisoprene (PI-OH) the same as in example 1.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as example 1, except that 0.95g of the linear hydroxylated polyisoprene (PI-OH) prepared in step (2) is added according to the molar ratio of the lactide monomer to the hydroxyl group of 80, and the product, linear comb-shaped polylactic acid, has a number average molecular weight of 23.2X 10 by GPC analysis4And PDI is 1.09.
Example 4
(1) Preparation of Polyisoprene (PI) and (2) preparation of Linear hydroxylated Polyisoprene (PI-OH) the same as in example 1.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as example 1, except that 1.26g of the linear hydroxylated polyisoprene (PI-OH) prepared in step (2) is added according to the molar ratio of the lactide monomer to the hydroxyl group of 60, and the product linear comb-shaped polylactic acid has a number average molecular weight of 15.9X 10 by GPC analysis4And PDI is 1.17.
Example 5
(1) Preparation of Polyisoprene (PI) and (2) preparation of Linear hydroxylated Polyisoprene (PI-OH) the same as in example 1.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as example 1, except that 0.19g of the linear hydroxylated polyisoprene (PI-OH) prepared in step (2) is added according to the molar ratio of the lactide monomer to the hydroxyl of 400, and the product, linear comb-shaped polylactic acid, has a number average molecular weight of 99.64X 10 by GPC analysis4And PDI is 1.15.
Example 6
(1) Polyisoprene (PI) was prepared as in example 1.
(2) Preparation of Linear hydroxylated Polyisoprene (PI-OH)
The preparation method is the same as example 1, except that the molar ratio of Polyisoprene (PI) to mercaptoalkyl alcohol (RSH) is [ PI ]]0and/RSH is 0.2: 1. The linear hydroxylated polyisoprene (PI-OH) was analyzed by the test to have a degree of hydroxylation of 33.9%, a hydroxyl number of 31, a number average molecular weight of 6760(GPC test), and a PDI of 1.06.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as that of example 1, except that the linear hydroxylated polyisoprene in example 1 is replaced by the linear hydroxylated polyisoprene (PI-OH) obtained in step (2) in the example, 0.82g of the linear hydroxylated polyisoprene (PI-OH) obtained in step (2) is added according to the molar ratio of lactide monomer to hydroxyl of 60, and the product linear comb-shaped polylactic acid has a number average molecular weight of 27.64 × 10 by GPC analysis4And PDI is 1.10.
Example 7
(1) Polyisoprene (PI) was prepared as in example 1.
(2) Preparation of Linear hydroxylated Polyisoprene (PI-OH)
The preparation method is the same as example 1, except that the molar ratio of Polyisoprene (PI) to mercaptoalkyl alcohol (RSH) is [ PI ]]0and/RSH 15: 1. The test analysis showed that the linear hydroxylated polyisoprene (PI-OH) had a degree of hydroxylation of 27.3%, a hydroxyl number of 26, a number average molecular weight of 6870(GPC test) and a PDI of 1.06.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as that of example 1, except that the linear hydroxylated polyisoprene in example 1 is replaced by the linear hydroxylated polyisoprene (PI-OH) obtained in step (2) in the example, 0.99g of the linear hydroxylated polyisoprene (PI-OH) obtained in step (2) is added according to the molar ratio of lactide monomer to hydroxyl of 60, and the product linear comb-shaped polylactic acid has a number average molecular weight of 22.3 × 10 by GPC analysis4And PDI is 1.11.
Example 8
(1) Preparation of Polyisoprene (PI)
The preparation method was the same as in example 1, except that 150mL of the mixed solvent of tetrahydrofuran and n-hexane having a volume ratio of 1:4 of tetrahydrofuran to n-hexane was replaced with 150mL of the n-hexane solvent. The product Polyisoprene (PI) has a number average molecular weight of 0.62X 104The molecular weight distribution (PDI) was 1.03, 1, 2-polymerization 1 wt%, 3, 4-polymerization 33.8 wt%, 1, 4-polymerization 65.2 wt%.
(2) Preparation of Linear hydroxylated Polyisoprene (PI-OH)
The preparation method is the same as that of example 1, except that the polyisoprene in example 1 is replaced by the Polyisoprene (PI) obtained in step (1) of this example. The obtained linear hydroxylated polyisoprene (PI-OH) was analyzed by the test to have a degree of hydroxylation of 8%, a hydroxyl number of 7.6, a number average molecular weight of 6300(GPC test), and a PDI of 1.04.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as that of example 1, except that the linear hydroxylated polyisoprene in example 1 is replaced by the linear hydroxylated polyisoprene (PI-OH) obtained in step (2) in this example, 0.31g of the linear hydroxylated polyisoprene (PI-OH) obtained in step (2) is added in a molar ratio of lactide monomer to hydroxyl of 600, and the product linear comb-shaped polylactic acid has a number average molecular weight of 64.1 × 10 as determined by GPC analysis4And PDI is 1.13.
Example 9
(1) Preparation of Polyisoprene (PI) and (2) preparation of Linear hydroxylated Polyisoprene (PI-OH) example 8 was followed.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as example 8, except that 0.23g of the linear hydroxylated polyisoprene (PI-OH) prepared in step (2) is added according to the molar ratio of the lactide monomer to the hydroxyl group of 800, and the product, linear comb-shaped polylactic acid, has a number average molecular weight of 81.1X 10 by GPC analysis4And PDI is 1.15.
Comparative example 1
(1) Polyisoprene (PI) was prepared as in example 1.
(2) Preparation of Linear hydroxylated Polyisoprene (PI-OH)
The preparation method is the same as example 1, except that the molar ratio of Polyisoprene (PI) to mercaptoalkyl alcohol (RSH) is [ PI ]]0and/RSH 70: 1. The linear hydroxylated polyisoprene (PI-OH) was analyzed by the test to have a degree of hydroxylation of 2.6%, a hydroxyl number of 2.4, a number average molecular weight of 6210(GPC test) and a PDI of 1.03.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as example 1, except that the linear hydroxylated polyisoprene in example 1 is replaced by the linear hydroxylated polyisoprene (PI-OH) obtained in step (2) of the present comparative example, and 9.7g of the linear hydroxylated polyisoprene (PI-OH) obtained in step (2) is added in a molar ratio of lactide monomer to hydroxyl of 60, and the product linear comb-shaped polylactic acid has a number average molecular weight of 2.1 × 10 by GPC analysis4And PDI is 1.10.
Comparative example 2
(1) Preparation of Polyisoprene (PI) and (2) preparation of Linear hydroxylated Polyisoprene (PI-OH) the same as in example 1.
(3) Preparation of linear comb-shaped polylactic acid
The preparation method is the same as example 1, except that 0.08g of the linear hydroxylated polyisoprene (PI-OH) prepared in step (2) is added according to the molar ratio of the lactide monomer to the hydroxyl group of 900, and the product linear comb-shaped polylactic acid has a number average molecular weight of 73.9X 10 by GPC analysis4And PDI is 1.6.
As can be seen from examples 1 to 9 and comparative examples 1 to 2, the linear comb-shaped polylactic acid prepared by the present invention has characteristics of high molecular weight, narrow distribution and highly branched structure. The preparation method has simple process, stable preparation process and controllable reaction process, and can adjust the molecular weight and the proportion of the main chain and the side chain of the linear comb-shaped polylactic acid by controlling the reaction conditions.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (33)
1. A linear comb-shaped polylactic acid has a molecular structure shown in formula (I):
wherein R is1Selected from hydrogen or C1-C6Alkyl groups of (a);
R2is selected from C2-C5An alkylene group of (a);
x, y, z, m and n are positive integers,
the linear comb-shaped polylactic acid is prepared according to the following method:
s1, preparing polyisoprene through anionic polymerization;
s2, carrying out click reaction on the polyisoprene prepared in the S1) and mercaptoalkyl alcohol to prepare linear hydroxylated polyisoprene;
s3, carrying out polymerization reaction on the linear hydroxylated polyisoprene prepared in the S2) and lactide monomer to prepare linear comb-shaped polylactic acid;
the molar ratio of the polyisoprene to the mercaptoalkyl alcohol is (0.1-60): 1.
2. The linear comb polylactic acid according to claim 1, wherein R is1Selected from hydrogen, methyl, ethyl or propyl.
3. The linear comb polylactic acid according to claim 1, which isCharacterized in that R1Selected from methyl.
4. The linear comb polylactic acid according to claim 1, wherein R is2Selected from ethylene or propylene.
5. The linear comb polylactic acid according to claim 1, wherein R2 is selected from ethylene.
6. The linear comb-shaped polylactic acid according to claim 1, wherein the number average molecular weight of the linear comb-shaped polylactic acid is (0.1-100). times.104。
7. The linear comb-shaped polylactic acid according to claim 1, wherein the number average molecular weight of the linear comb-shaped polylactic acid is (1-50) × 104。
8. The linear comb polylactic acid according to any one of claims 1 to 7, wherein the molecular weight distribution index of the linear comb polylactic acid is 1.05 to 1.4.
9. The linear comb polylactic acid according to claim 8, wherein the molecular weight distribution index of the linear comb polylactic acid is 1.05 to 1.2.
10. A method for preparing the linear comb-shaped polylactic acid according to any one of claims 1 to 9, which comprises the following steps:
s1, under the action of the initiator A, carrying out anionic polymerization on an isoprene monomer to prepare polyisoprene;
s2, under the protection of inert gas, enabling polyisoprene and mercaptoalkyl alcohol to perform click reaction under the action of an initiator B to prepare linear hydroxylated polyisoprene;
s3, under the protection of inert gas, carrying out polymerization reaction on linear hydroxylated polyisoprene and lactide monomer under the action of a catalyst to prepare linear comb-shaped polylactic acid;
wherein the linear hydroxylated polyisoprene has a hydroxyl number of 3 to 260.
11. The method of claim 10, wherein the linear hydroxylated polyisoprene has a hydroxyl number of 10 to 180.
12. The method of claim 10, wherein the linear hydroxylated polyisoprene has a hydroxyl number of 19 to 100.
13. The method of claim 10, wherein the linear hydroxylated polyisoprene has a number average molecular weight of (0.05-3.5) x 104。
14. The method of claim 13, wherein the linear hydroxylated polyisoprene has a number average molecular weight of (0.1 to 3). times.104。
15. The method of claim 14, wherein the linear hydroxylated polyisoprene has a number average molecular weight of (0.2-1.5) x 104。
16. The method according to claim 10, wherein in step S1, the polymerization reaction is carried out at a reaction temperature of 0 to 50 ℃ for a reaction time of 0.5 to 12 hours;
the molar ratio of the initiator A to the isoprene is (2 x 10)-3-0.1):1；
The initiator A is a compound shown in a formula II,
R3li (formula II)
In the formula (II), R3Is selected from C1-C6Alkyl of (C)3-C12Cycloalkyl of, C6-C12Aryl or C of7-C14An aralkyl group of (2).
17. The method according to claim 10, wherein the initiator a is at least one selected from the group consisting of ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, phenyllithium, 2-naphthyllithium, 4-butylphenyl lithium, 4-methylphenyllithium, cyclohexyllithium, and 4-butylcyclohexyllithium;
the polyisoprene has a number average molecular weight of (0.05-3). times.104The content of the double bond of the side chain is 35 to 85 percent.
18. The method according to claim 10, wherein in step S1, the polymerization reaction is carried out in a solvent of n-hexane and/or tetrahydrofuran.
19. The production method according to claim 18, wherein in step S1, the polymerization reaction is carried out in a mixed solvent of n-hexane and tetrahydrofuran, and the volume ratio of tetrahydrofuran to n-hexane in the mixed solvent is 1:30 to 30: 1.
20. The method according to claim 10, wherein in step S2, the click reaction is performed at a reaction temperature of 60 to 70 ℃ for a reaction time of 12 to 24 hours;
the initiator B is a thermal decomposition type free radical initiator.
21. The production method according to claim 10, wherein the initiator B is at least one selected from the group consisting of peroxide initiators and azobisnitrile initiators.
22. The production method according to claim 10, wherein the initiator B is at least one selected from the group consisting of diacyl peroxides, peroxydicarbonates, peroxycarboxylates, alkyl peroxides, and azobisnitrile compounds.
23. The method according to claim 10, wherein the initiator B is at least one selected from the group consisting of dibenzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, di-o-methylbenzoyl peroxide, tert-butyl peroxybenzoate, dicumyl peroxide, azobisisobutyronitrile, and azobisisoheptonitrile.
24. The method according to claim 1, wherein in step S2, the molar ratio of the polyisoprene to the mercaptoalkyl alcohol is (0.2-40): 1.
25. The method according to claim 1, wherein the molar ratio of the polyisoprene to the mercaptoalkyl alcohol is (0.5-30): 1.
26. The preparation method according to claim 10, wherein the molar ratio of the initiator B to the polyisoprene is (0.1-0.8): 1.
27. The preparation method according to claim 10, wherein the molar ratio of the initiator B to the polyisoprene is (0.2-0.5): 1.
28. The method according to claim 10, wherein in step S3, the molar ratio of the lactide monomer to the hydroxyl group in the linear hydroxylated polyisoprene is 5 to 800; the molar ratio of the lactide monomer to the catalyst is 300-9000; the catalyst is at least one of tin powder, inorganic salt of tin, organic salt of tin, antimony oxide, organic acid rare earth compound and iron compound.
29. The method of claim 10, wherein the molar ratio of lactide monomer to hydroxyl groups in the linear hydroxylated polyisoprene is 10 to 600.
30. The method as claimed in claim 10, wherein the molar ratio of lactide monomer to catalyst is 800-6000.
31. The method according to claim 10, wherein the catalyst is at least one selected from the group consisting of tin powder, stannous chloride, stannous octoate, stannous benzoate, and antimony trioxide.
32. The method according to claim 1, wherein the lactide monomer is selected from one or more of L-lactide, D-lactide, and DL-lactide.
33. The method as claimed in claim 1, wherein in step S3, the polymerization reaction temperature is 110-140 ℃ and the reaction time is 1-6 h.
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| CN102964580A (en) * | 2012-10-31 | 2013-03-13 | 大连理工大学 | Linear comb polylactic acid and preparation method thereof |
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| CN102336914A (en) * | 2011-07-06 | 2012-02-01 | 浙江大学 | Amphipathy graft copolymer of polyisoprene and polyethylene glycol and preparation method and usage thereof |
| CN102964580A (en) * | 2012-10-31 | 2013-03-13 | 大连理工大学 | Linear comb polylactic acid and preparation method thereof |
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