Construction And Regulation Of Two-Dimensional Ordered Structure In Side-Chain Liquid Crystalline Polymers

Two-dimensional ordered columnar liquid crystal is a very important class of liquid crystal in the ordered structure of soft matter,which is commonly seen in block copolymer,amphiphilic molecule,disk liquid crystal and other systems.Through the precise design of side-chain structure of polymer,side-chain liquid crystalline polymer can also form supramolecular two-dimensional ordered columnar structure.In this paper,we first studied the construction of a new class of supramolecular columnar phase,and studied the transformation relationship between different columnar phases by copolymerization.Finally,we studied the unique advantages of columnar phase in the construction of complex surface morphology of block copolymer thin films.This paper mainly includes the following contents:1.A series of styrenic liquid crystalline monomers St-n-23（n=2,6,8,10,12）have two substituent mesogenic groups attached to a phenyl ring at the 2 and 3 positions substituent positions and their polymers were synthesized.It was found that all polymers can self-assemble to form two-dimensional ordered supramolecular oblique symmetry columnar(Col_ob/p2)structure.With the increase of temperature,the Col_ob/p2-to-lamellar phase transition appears,and finally into isotropic phase.With the increase of the length of the flexible spacer,the clearing temperature（Ti）of PS-n23 decreases gradually,and the phase structure parameters can be adjusted with the flexible spacer.In addition,simple shearing can produce polymer thin films with very good orientation of the columnar phase at the macroscopic scale.2.A（2,3 positions）,E（3,4 positions）and D（3,4,5 positions）of three kinds of liquid crystalline monomers with different positions and numbers of substitutions on the central benzene ring were copolymerized respectively.Three series of copolymers of A-r-D,E-r-D and A-r-E were obtained,and the effect of comonomer content on the liquid crystalline structure of the copolymers was studied.The homopolymers corresponding to monomer A and E can form Col_ob/p2 structure.The homopolymer D is Col_hex structure.With the increase of the mole percentage of D,the self-assembly structure of copolymer A-r-D follows the sequence from Col_ob/p2 to undulated lamellar,lamellar,and Col_hex structures.With increasing molar content of D,the selforganzied structure of copolymer E-r-D follows the sequence from Col_ob/p2 to intermediate phase,and Col_hex structures.The copolymers with intermediate phase first developed into Col_ob/p2 structure then entered the Col_hex phase,and finally became amorphous phase.For copolymer A-r-E,with the increase of the mole percentage of E,the self-assembly structure of the copolymer always maintains the Col_ob/p2 structure,and the structure parameters can be adjusted with the composition.The self-assembly structure and phase behavior of the copolymer can be regulated by changing the composition of the two monomers in the copolymer.By copolymerization,the mutual transformation law between different two-dimensional ordered columnar phases was obtained.3.Conventional liquid crystalline block copolymer thin films have simple surface morphology and single size.We investigated the surface morphology of supramolecular liquid crystalline block copolymer PS-b-P4VP（BP）_x thin films by introducing Col_hex structure P4VP（BP）_x into the block copolymer system.When x>0.3,the surface of supramolecular block copolymer thin film can be spontaneously covered with two regular patterns with different periodicities,which are associated with parallel small cylinder from P4VP（BP）block（7.8 nm）and perpendicular large lamellae or cylinder formed by block copolymer（40～50 nm）.This is different from the multi-size hierarchical structure of "structure within structure" formed by the bulk sample,and the small size pattern also covers the surface of the copolymer thin film.Water contact angle and XPS studies show that P4VP（BP）block with lower interfacial energy tend to aggregate on the surface of thin films,resulting in a unique surface nanopattern of liquid crystalline ordered and block copolymer microphase separation.