Photodeformable polymer gels and crosslinked liquid-crystalline polymers

Abstract

Both polymer gels and crosslinked liquid-crystalline polymers (CLCPs) have unique properties to be developed as stimuli-responsive soft materials. While the former are suitable to be used in a wet circumstance, the latter are able to be applied as dry actuation materials. Among various stimulating sources, light has attracted more interest because it is a kind of clean energy which can be manipulated conveniently and controlled in situ. Photodeformable polymer gels and CLCPs undergo macroscopic shape changes such as contraction and bending induced by light, thus providing a photomechanical effect. This review will describe the advances in the field of photomanipulation regarding both the polymer gels and the CLCPs including the design of these smart materials, controlled actuation in response to light, and ability to tailor the materials properties for different applications.

Stimuli-responsive photonic polymer coatings

“…Usually, the materials for such coatings are based on liquid crystalline (LC) polymers or hydrogels and solvent gels (Scheme 1). [17][18][19] Small changes in the molecular order of LC materials can lead to large dimensional changes (Scheme 1a). 20,21 Volumetric and dimensional changes in gels are based on differences in swelling and shrinkage due to the adsorption or desorption of a solvent (Scheme 1b).…”

New strategies and implications for the photoalignment of liquid crystalline polymers

“…This approach has provided various types of smart, light-responsive materials 1 exhibiting surface-mediated photoalignment of LC materials, [2][3][4][5][6] photoinduced phase transitions, [7][8][9][10][11][12] photoorientation/addressing of polymer thin films, [13][14][15][16][17][18] photoinduced mass migrations, [19][20][21][22][23][24][25][26][27][28] phototactic sliding motions, [29][30][31] photo-driven motions and morphology of monolayers, [32][33][34][35] and macroscopic photomechanical deformations. [36][37][38][39][40][41][42][43][44][45][46] Photoalignment research and technology started in 1988 with the discovery of the reversible alignment control of nematic LCs by the photoisomerization of azobenzene on a substrate surface (Figure 1) by Ichimura et al …”

“…Considering this point, the development of methods for controlling materials at the mesoscopic level should be meaningful and alluring because of the material chemistry. Mesoscopic systems are expected to bridge the photoresponsive phenomena of different size ranges between molecular [75][76][77] and macroscopic functions [36][37][38][39][40][41][42][43][44][45][46] and provide panoscopic views of photoresponsive smart materials. …”

“…This approach has provided various types of smart, light-responsive materials 1 exhibiting surface-mediated photoalignment of LC materials, 2-6 photoinduced phase transitions, 7-12 photoorientation/addressing of polymer thin films, 13-18 photoinduced mass migrations, [19][20][21][22][23][24][25][26][27][28] phototactic sliding motions, 29-31 photo-driven motions and morphology of monolayers, 32-35 and macroscopic photomechanical deformations. [36][37][38][39][40][41][42][43][44][45][46] Photoalignment research and technology started in 1988 with the discovery of the reversible alignment control of nematic LCs by the photoisomerization of azobenzene on a substrate surface (Figure 1) by Ichimura et al 47 It was demonstrated that the E/Z (trans/cis) photoisomerization of an azobenzene monolayer on a substrate can switch the alignment of nematic LC molecules between the homeotropic and planar modes. This active functional surface was dubbed a 'command surface' or 'command layer.'…”

Textures and shapes in nematic elastomers under the action of dopant concentration gradients

“…Further theoretical models envisage the use of repeated reshaping for propelling nematoelastic walkers [25,26] and swimmers [27]. Other reshaping effects were explored to produce the various bent forms that may serve as actuators [28][29][30][31][32] and "4D-printing" of structures variable in time [33].…”