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A novel series of hard‐soft‐hard triblock azo‐copolymers (TBCs) composed of poly(2‐[2‐(4‐cyano‐azobenzene‐4‐oxy)ethylene‐oxy]ethyl methacrylate) (PCEAMA), poly(methyl methacrylate) (PMMA) and poly(p‐dodecylphenyl‐N‐acrylamide) (PDOPAM) were synthesized by employing reversible addition‐fragmentation chain transfer polymerization. Chemical structures and molecular weights were characterized by 1H nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Thermal behavior, mesophase, photochemistry and morphology were investigated using differential scanning calorimetry (DSC), optical polarizing microscopy (OPM), ultraviolet–visible spectrophotometry (UV–vis), atomic force microscopy (AFM) and grazing‐incidence small‐angle X‐ray scattering (GISAXS). Kinetic studies confirmed characteristic of controlled/living radical polymerization with low polydispersities (≤1.40). TBCs manifested both endothermic and exothermic transition peaks assigned to smectic to nematic, nematic to smectic, and smectic‐A to smectic‐C phases. TBCs having hight azo fractions of 39 and 34 wt % revealed textures of smectic phase whereas TBC possessing 30 wt % of azo content exhibited poor texture, suggesting nematic phase. Regarding TBC with low azo ratio (25 wt %), neither mesophase texture was found. All TBCs showed photoresponsive behavior under UV–vis irradiation or thermal relaxation. TBC‐1 with PCAEMA (39 wt %), PMMA (40 wt %) and PDOPAM (21 wt %) generated a mixture of cylinder and lamellar nanostructures compared to TBC‐2 and TBC‐3 which formed lamellae. However, TBC‐4 having the highest PDOPAM fraction (50 wt %) produced hexagonal cylindrical nanostructure. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1617–1629

Reversible addition–fragmentation chain transfer polymerization is employed for the preparation of a series of novel ABC-type azo triblock copolymers (TBCs) consisting of poly­(CAEMA), poly­(BMA), and poly­(DOPAM) using AIBN as an initiator and anisole as a solvent. The TBCs are characterized by means of 1H nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Their mesophase, photoresponsive, and morphological behaviors are examined using differential scanning calorimetry (DSC), optical polarizing microscopy (OPM), ultraviolet–visible spectrophotometry (UV–vis), atomic force microscopy (AFM), and grazing-incidence small-angle X-ray scattering (GISAXS). Molecular weights and polydispersities (≤1.38) increase slightly with the increase of the molar ratio of monomer to macroinitiator, confirming a controlled/living radical polymerization. All TBCs demonstrated endothermic and exothermic transition peaks corresponding to the smectic-to-nematic and nematic-to-smectic phases. Thermal investigation revealed that the TBCs containing 54 and 46 wt % of azo contents displayed batonnet textures of smectic phase, while the TBC with low azo block fraction of 39 wt % showed threaded texture of nematic phase. For TBC having the lowest azo content of 31 wt %, neither liquid crystalline texture is detected. TBC-2 with 46 wt % of azo block, 28 wt % of PBMA, and 26 wt % of PDOPAM produced a lamellar compared to TBC-1 and TBC-3 which formed a mixture of cylinder and lamellar morphologies. Contrastingly, TBC-4 containing the highest PDOPAM volume ratio of 50 wt % generated hexagonal cylinder-type morphology. All TBCs exhibited a reversible trans–cis–trans photoisomerization behavior in chloroform solution and in thin film under UV and visible light irradiation (or dark storage) at varied intervals of time.

A series of azo-based diblock copolymers (DBCs) with various compositions were successfully synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization in anisole with PCAEMA-CTA (macro-CTA), DOPAM (new acrylamide monomer) and AIBN (initiator). Kinetic studies on diblock copolymerization manifested a controlled/living manner with good molecular weight control. Structures and properties of monomers and DBCs were determined by 1 H nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). Liquid crystalline (LC) phases and morphological properties were investigated using optical polarizing microscope (OPM), atomic force microscopy (AFM), scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS). Experimental results demonstrated that the prepared PCAEMA-CTA and DBCs possessed low polydispersity index (≤1.37). All DBCs revealed sharp endothermic transition peaks corresponding to the smectic-to-nematic phase. DBCs with high azo contents showed batonnet textures of the smectic phase whereas DBCs of low azo segments displayed threaded textures of the nematic phase. DBC with 49 wt% of azo side-chains generated a lamellar compared to DBCs with low azo block (≤41 wt%) or nonazo block (≤38 wt%) which produced hexagonal-type nanostructures. In addition, all DBCs exhibited reversible trans-cis photoisomerization behavior under UV irradiation and dark storage at different intervals of time.

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