Synthesis of novel three‐arm star azo side‐chain liquid crystalline polymer via ATRP and photoinduced surface relief gratings

Abstract

A three‐arm star azo side‐chain liquid crystalline (LC) homopolymer, poly[6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate] (PMMAZO), was synthesized by atom transfer radical polymerization (ATRP) method. The polymerization of 6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate proceeded in a controlled/“living” way. A series of three‐arm star LC block copolymers (PMMAZO‐b‐PMMA) were also synthesized. The polymers were characterized by 1H NMR, gel permeation chromatograph, and UV–vis spectra, respectively. The both polymers of PMMAZO and copolymers of PMMAZO‐b‐PMMA exhibited a smetic phase and a nematic phase. As concern to the PMMAZO, the glass‐transition temperature (Tg) and phase‐transition temperature from the smetic to nematic phase and from the nematic to isotropic phase increased with the increase of molecular weight (Mn(GPC)) of PMMAZO. The phase transition temperature of the block copolymers, PMMAZO‐b‐PMMA, with the same PMMA block was similar to that of PMMAZO. However, the Tg of the PMMAZO‐b‐PMMA decreased at low azo content and then increased with the increasing Mn(GPC) when azo content was above 61.3%. With illumination of linearly polarized Kr+ laser beam at modest intensities (35 mW/cm2), significant surface relief gratings formed on PMMAZO films with different molecular weights were observed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 777–789, 2008

Synthesis and photoresponsive behavior of the high-Tg azobenzene polymers via RAFT polymerization

“…Permitting precise control over the polymerization process, they have provided a new set of robust methods for pre-designed polymers. Azobenzene polymers with well controlled molecular weights and structures have been easily synthesized via living free radical polymerization [40][41][42][43][44][45]. However, the majority of reported side-chain azobenzene polymers had low T g s which did not favor these materials in high temperature applications.…”

Synthesis and characterization of photoactive poly(arylene ether sulfone)s containing azobenzene moieties in their main chains

“…Polymers bearing azobenzene moieties (azo-polymers) are fascinating materials and have attracted considerable attention in recent years because of their unique reversible photo-isomerization and photoinduced anisotropy properties [3][4][5][6][7][8]. The photoinduced isomerization and anisotropy can cause significant bulk, surface property variation and polarity of the polymers, such as photoinduced phase transition, photoinduced surface relief gratings (SRGs) and photoinduced birefringence [9][10][11][12][13][14][15], which show potential applications in fields such as optical data storage, optical switching and nonlinear optical materials [16][17][18][19][20][21][22][23]. In order to increase the optical stability for long-term applications, many efforts have been made to design and synthesize new high-T g aromatic azo-polymers, such as polyacrylate containing fully aromatic azo side chains and azo-polyimides.…”

Mechanism study and molecular design in controlled/“living” radical polymerization

“…ATRPs of different monomers as indicated in Figure 15, including lauryl methacrylate [87], hexadecyl acrylate [88], glycidyl methacrylate (GMA) [89], 6-(4-phenylazophenoxy) hexylmethacrylate [90], and 6-(4-methoxy-4-oxy-azobenzene) hexyl methacrylate [91], were carried out and functional homopolymers were obtained. The results showed wellcontrolled polymerization behaviors for all the monomers: a linear molecular weight increase with monomer conversion and narrow molecular weight distributions.…”

“…Anthraquinone [92], naphthalene [93], nitro [94] and azobenzene [91][92][93][94][95] groups were introduced into PS or PMMA chain by this method using ATRP. The polymerization showed controlled characteristics in those initiator systems with functional groups except for the nitro group.…”