Photoactive Thermoplastic Elastomers of Azobenzene-Containing Triblock Copolymers Prepared through Atom Transfer Radical Polymerization

Abstract

Atom transfer radical polymerization (ATRP) was used to prepare a new series of ABA triblock copolymers that are photoactive thermoplastic elastomers. The samples synthesized have the same rubbery midblock of poly(n-butyl acrylate) (PnBA) but differ in the degree of polymerization of the end blocks of a methacrylate-based azobenzene-containing side-chain liquid crystalline polymer (Azo-SCLCP). The coupling between elasticity, liquid crystallinity and photoactivity imparts interesting features to this type of thermoplastic elastomers. When the solution-cast film is stretched at T > T g of the Azo-SCLCP whose microdomains act as physical cross-links, in contrast to conventional thermoplastic elastomers (such as styrene−butadiene−styrene triblock copolymer) that lose the elasticity, liquid crystalline microdomains can support part of the elastic extension of PnBA chains and, in the same time, deform to result in a long-range orientation of azobenzene mesogens. The liquid crystal orientation is retained in the relaxed film at T < T g, which creates a thermoplastic elastomer whose glassy microdomains contain oriented azobenzene mesogens. Moreover, the reversible trans−cis photoisomerization of the azobenzene chromophore can be used to modulate the mechanically induced orientation.

Macroscopic Parallel Nanocylinder Array Fabrication Using a Simple Rubbing Technique

“…[2][3][4] Furthermore, periodic nanostructures may be formed by the interplay processes between the microphase separation and the regular periodicity of LC ordering, [5,6] which are known as supramolecular cooperative motions (SMCMs). It is widely known that ordered microphase structures can be formed in well-defined block copolymers, [7][8][9][10][11][12][13][14][15][16] which can be used as templates for the fabrication of novel nanostructured materials.…”

Light‐Responsive Block Copolymers

“…[75,82,83] Some interesting features involving holographic gratings on elastic materials have been reported. [84][85][86][87][88] In those studies, the well-known thermoplastic elastomer polystyrene-block-polybutadiene-block-polystyrene (SBS) has been used. When the PS content is equal to 20-30%, the microphase separation provides PS nanocylinders which act as crosslinkers for the rubbery PB chains.…”

Azobenzene-Containing Materials for Hologram

“…By the stretching, diffraction efficiency of the gratings was adjusted accordingly . Recently, mechanically tunable fringe spacing was also obtained in gratings recorded with ABA-type triblock copolymers showing properties of conventional thermoplastic elastomers, in which rubbery poly(n-butyl acrylate) was designed as middle soft block and photoresponsive polymers acted as hard block (Cui et al, 2004).…”