CN113650329B

CN113650329B - Preparation method and application of non-reciprocal chiral flexible film

Info

Publication number: CN113650329B
Application number: CN202110786993.XA
Authority: CN
Inventors: 邓建平; 李鹏鹏; 潘凯
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2021-07-12
Filing date: 2021-07-12
Publication date: 2023-06-13
Anticipated expiration: 2041-07-12
Also published as: CN113650329A

Abstract

A preparation method and application of a non-reciprocal chiral flexible film belong to the technical field of chiral films. The prepared chiral spiral polymer and the elastomer polymer are blended according to a certain proportion to prepare a spin coating solution by utilizing a spin coating method, spin coating parameters are regulated to obtain a transparent and stretchable chiral flexible film with excellent mechanical properties, the film can be subjected to simple stretching treatment to have excellent non-dissimilar circular polarization absorption characteristics, and the chiral asymmetric strength of the stretched film can be flexibly regulated and controlled by controlling the elongation and recovery rate of the stretched film.

Description

Preparation method and application of non-reciprocal chiral flexible film

Technical Field

The invention relates to preparation of a non-dissimilarity chiral flexible film and application related to adjustable chiral asymmetric strength, which are a method for preparing the non-dissimilarity chiral flexible film by utilizing a conventional spin coating technology and simple stretching treatment, and realize accurate adjustment and control of dissymmetry of material chirality and strength thereof, and belong to the chiral field.

Background

Chiral molecules exist widely in nature and can be represented on structures of different scales and different levels, such as chiral polymers and chiral molecules. The use of such smart chiral materials in chiral electronics and photonics would be easy if the external stimulus response could be utilized to precisely control the chirality of the material. Switchable chiral materials offer advantages in adjusting left and right hand optical activity or chiral switching, and have attracted considerable attention in the field of materials science.

Nonreciprocal is a term in the art of microwave technology and materials that refers to the property that electromagnetic waves transmitted in opposite directions in an object exhibit different electromagnetic losses, phase shifts, etc., and this phenomenon is referred to as nonreciprocal. The non-dissimilarity material mentioned in the field of chiral materials, which is exemplified by a thin film material, means that when racemic circularly polarized light passes through two sides of a thin film sample, respectively, there is a difference in absorption of the circularly polarized light by two faces of the sample, and as a result, the circularly polarized light with almost completely opposite handedness, which is mainly single handedness, is obtained on both sides. Here, the wave vector of the emitted light propagates in the opposite direction with respect to the film surface. The material system has wide application prospect in the fields of chiral templates, encryption, information storage, optical display and the like. Currently, the potential mechanism of controlling chirality and studying chiral switching remains a very challenging task, but has important implications for understanding the origin of chirality and even creating new functional materials.

Although chiral switching-related materials have achieved significant achievements, the special structure of the existing research materials requires a complex preparation process, and the optical activity strength of the materials cannot be flexibly adjusted. In addition, these chiral materials do not easily achieve reversible adjustment of optical activity or asymmetric factor intensity while achieving chiral switching. Obtaining simple and thorough chiral manipulation in a stable and efficient manner is still very limited. Furthermore, chiral manipulation in solid materials (e.g., solid film materials) is also well suited for practical applications. In order to widen the application of the chiral polarizer in the chiral optical and electronic fields, the development of a circular polarization system for realizing switchable chirality in a single solid film is urgent.

From the practical point of view, we have urgent need for a solid material which has simple process flow, flexible chiral switching and arbitrarily adjustable asymmetric strength and can be prepared on a large scale. Here we report a flexible, spin-coated film that allows asymmetric switchable circular polarization absorption or emission in a single object by simply flipping the stretched film.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a preparation method and application of a non-reciprocal chiral flexible film. The technical scheme is as follows:

in order to achieve the above purpose, the invention provides a preparation method and application of a non-reciprocal chiral flexible film: the method utilizes a conventional spin coating method to prepare a spin coating solution by blending chiral spiral polymer and elastomer polymer according to a certain proportion, adjusts spin coating parameters and film forming temperature to prepare a transparent and stretchable chiral flexible film, and can realize non-dissimilarity circular polarization absorption from the front side and the back side of the film through simple stretching treatment. Further, the chiral asymmetric strength of the film can be flexibly adjusted by controlling the elongation and the recovery rate of the film.

The method specifically comprises the following steps:

(1) Preparing a spin coating solution: weighing a certain amount of chiral spiral polymer, adding the chiral spiral polymer into a proper amount of elastomer polymer matrix solution, and fully stirring and dissolving to obtain a spin-coating solution for preparing a chiral film;

(2) Preparing a chiral flexible film: taking a proper amount of spin coating solution, carrying out spin coating by using a spin coater (spin coater), using a round glass sheet as a carrier, controlling spin coating parameters, and putting the spin-coated wet film body and the glass sheet into an oven for drying; finally, the dried film is peeled off from the glass substrate to obtain the chiral flexible film.

(3) Application of regulatable non-dissimilarity chiral film material: for ease of understanding and independent measurement of the asymmetric absorption of circularly polarized light from both sides of the film, the side in contact with air during spin-coating film formation is defined as the "upper surface", and the side in contact with the glass substrate is defined as the "lower surface" (see fig. 3). A bi-directional circular dichroism test method was then established and circular dichroism was measured from both sides of the same film: the front side (upper surface tested against the light source) and the back side (lower surface tested against the light source) were recorded (see fig. 4). The circular polarization absorption with non-mutually opposite front and back sides can be realized by simple stretching treatment of the chiral flexible film. The chiral asymmetry strength of the film is flexibly regulated and controlled by further controlling the elongation of the stretched film.

Specifically, the chiral helical polymer comprises polyacetylenes, polymethacrylates, polyisocyanates, polychloroacetals, polysilanes, polyisocyanides and the like. Preferably a chiral helix substituted polyacetylene.

The elastomer matrix in the step (1) is selected from one of TPU, PDMS, SBS and other polymers. Thermoplastic polyurethane elastomer rubber (TPU) is preferred.

The solvent used for the polymer matrix solution includes N, N-Dimethylformamide (DMF), o-xylene (OX), dimethyl sulfoxide (DMSO), N-dimethylacetamide (DMAc), tetrahydrofuran (THF), toluene and chloroform (CHCl) ₃ ) One or more of the following; preferably a mixed solution of N, N-Dimethylformamide (DMF) and Tetrahydrofuran (THF).

The content of the chiral helical polymer and the elastomer polymer matrix in the spin coating solution is 5mg/mL to 50mg/mL and 100mg/mL to 300mg/mL respectively.

And (2) spin coating parameters, namely spin coating at a low speed of 300r/min-800r/min for 5s-20s, spin coating at a high speed of 1000r/min-3000r/min for 5s-20s, and drying at a temperature of 30-60 ℃ in an oven, wherein the thickness of the spin coating film is 10-100 mu m.

The elongation of the chiral flexible film in the step (3) is controlled to be 10% -400%.

The chiral flexible film prepared by the invention has the characteristics of high mechanical property, extremely light weight, flexible stretching, controllable film thickness in a certain range and the like, can realize the characteristics of non-reciprocity and chiral adjustability in a stretchable solid material at the same time, represents a fundamental progress, and provides a new opportunity for the design, preparation and application of chiral optical materials.

Drawings

For a clearer description of the technical solutions in this embodiment, the drawings that are needed in the description of the embodiment are briefly introduced below, the drawings in the description are only some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a circular dichroism spectrum (A) and a corresponding ultraviolet absorption spectrum (B) of chiral helical substituted Polyacetylene (PSA) in an embodiment of the invention; dispersing the Polymer in CHCl ₃ In the above, the homogeneous solution was tested.

FIG. 2 is a digital photograph of a non-anisotropic chiral flexible film in an embodiment of the invention;

FIG. 3 is a schematic representation of the definition of the upper and lower surfaces of the spin-on film;

FIG. 4 is a schematic diagram of a bi-directional circular dichroism test method, defining the front and back sides during film testing;

FIG. 5 is a circular dichroism spectrum of a non-dissimilarity chiral flexible film provided in an embodiment of the present invention in (A) and in a dynamic stretched state (B) without any treatment; after the film is stretched to different elongations, the front and back sides of the film are subjected to a circular dichroism test, the test is performed at room temperature, and the instrument is not subjected to any change in the test process, so that the chiral film is only stretched.

Detailed Description

The present invention will be further described with reference to the following specific examples in order to make the objects and technical solutions of the present invention more apparent.

Example 1

The embodiment of the invention provides a preparation method and application of a non-dissimilarity chiral flexible film, and the specific operation steps comprise: related synthetic procedures for chiral helical substituted Polyacetylenes (PSAs) can be referred to (Biao Zhao, kai Pan, jianing deng.

24mg of chiral helical polymer PSA and 320mg of TPU were dissolved in 2mL of mixed solvent (DMF: thf=1:1, volume ratio), respectively, and magnetically stirred at 40 ℃ for a period of time until completely mixed and dissolved, to obtain a spin-on solution.

A round transparent glass sheet (diameter 10cm, thickness 1 mm) is always used as a coating substrate in the spin coating process; 2mL of the prepared spin coating solution was spin coated at a low speed of 600r/min for 15s, and then spin coated at a high speed of 1500r/min for 10s. The wet film was then placed in a vacuum oven with the glass substrate at 45 ℃ for 12 hours to allow the necessary solvent to evaporate completely. Finally, the dried film is peeled off from the glass plate to obtain the desired chiral flexible film. The chiral flexible film finally prepared is a uniform semitransparent film with the thickness of about 20 mu m.

And (3) carrying out dynamic stretching circular dichroism spectrum test on the obtained chiral flexible film, namely stretching the film to different degrees, carrying out circular dichroism test on the film in a stretching state, recording circular dichroism patterns of the front and back surfaces of the film under different elongations, and proving that the chiral flexible film has remarkable optical activity, and opening the non-dissimilarity characteristic of the film by stretching and realizing regulation and control on chiral asymmetric strength of the film by further regulating and controlling the elongation.

FIG. 5 is a schematic representation of a study of chiral helical polyacetylene with S-PSA, a chiral flexible film abbreviated as SCF-TPU-S-PSA ₈ (subscript 8 indicates 8% by weight of PSA in the TPU); the chiral film was tested from the front (dashed line) and back (solid line) for round dichroism when unstretchedThe spectrum is shown in figure a; the chiral flexible film was stretched to different elongations and the circular dichroism spectrum obtained from the front and back side test is shown in figure b, where SCF-TPU-S-PSA ₈ -x%, x representing the elongation of the film after stretching.

In summary, the embodiment of the invention provides a method for preparing a non-dissimilarity chiral flexible film by a spin-on film method, and the prepared chiral film is flexible, can be bent, curled and stretched greatly, and has excellent mechanical properties. The method is simple to operate, good in controllability, capable of realizing chiral non-intersectivity of the film through simple stretching treatment, capable of realizing chiral asymmetric intensity adjustment through adjusting and controlling the elongation of the stretched film, and suitable for chiral switchable materials and flexible circularly polarized luminescent materials.

The above examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. Further, any modifications, equivalents, improvements or modifications to the foregoing may occur to persons skilled in the art upon reading the teachings of the present invention.

Claims

1. The preparation method of the non-reciprocal chiral flexible film is characterized by comprising the following steps:

(1) Preparing a spin coating solution: weighing a certain amount of chiral spiral substituted polyacetylene, adding the chiral spiral substituted polyacetylene into a proper amount of thermoplastic polyurethane elastomer rubber (TPU) solution, and fully stirring and dissolving to obtain a spin-coating solution of the chiral flexible film;

(2) Preparing a chiral flexible film: taking a proper amount of spin coating solution, carrying out spin coating by using a spin coater or a spin coater, using a round glass sheet as a carrier, regulating spin coating parameters to carry out spin coating film making, and putting a spin-coated wet film body and the glass sheet into an oven for drying; finally, stripping the dried film from the glass substrate;

(3) Stretching the stripped film to obtain a non-reciprocal chiral flexible film, wherein the elongation is controlled to be 10% -400%; the non-reciprocal chiral flexible film shows non-reciprocal property of asymmetric circular polarization absorption after being stretched, namely, the film can absorb circularly polarized light with opposite dissymmetry from the front surface and the back surface of the film through simple stretching treatment; the chiral asymmetric strength of the film is flexibly adjusted by controlling the elongation and the recovery rate of the film;

the solvent used for the elastomer polymer matrix solution is a mixed solution of N, N-Dimethylformamide (DMF) and Tetrahydrofuran (THF);

the concentrations of the chiral helical polymer and the elastomer polymer matrix in the spin coating solution are 5mg/mL to 50mg/mL and 100mg/mL to 300mg/mL respectively;

and (2) spin coating parameters, namely spin coating at a low speed of 300r/min-800r/min for 5s-20s, spin coating at a high speed of 1000r/min-3000/min for 5s-20s, and drying at a temperature of 30-60 ℃ in an oven, wherein the thickness of the spin coating film is 10 [ mu ] m-100 [ mu ] m.

2. A non-reciprocal chiral flexible film made according to the method of claim 1.