The cyclic amphiphilic polymers with azobenzene in main chain, cyclic azobenzene tetraethylene glycol polystyrene (cyclic-Azo-TEG-PS) with different molecular weights, were successfully synthesized by combining atom transfer radical polymerization (ATRP) and Cu (I)-catalyzed azide/alkyne cycloaddition (CuAAC). Gel permeation chromatography (GPC), proton nuclear resonance (¹H NMR), Fourier transform-infrared (FT-IR), and matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry were used to prove the complete conversion from linear polymers to cyclic ones. The thermal properties and photoisomerization behaviors of obtained cyclic polymers have been investigated by comparison with the linear analogues. The cyclic polymer displayed a higher glass transition temperature compared with the linear one, measured by differential scanning calorimetry (DSC). It was found that the trans-to-cis and cis-to-trans isomerization of cyclic polymers was both slower than that of their respective linear counterparts upon irradiation by UV/visible light. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1834–1841

Two novel cyclic azobenzenophanes (SC, RC) with functional handles have been synthesized efficiently by a Glaser coupling reaction. Through a Suzuki coupling reaction, alternating ring/linear polymers with rigid (conjugated)/flexible (unconjugated) bridges were obtained from the resultant cyclic azobenzenophanes. The optical activities of linear, cyclic, and macromolecular binaphethyl–azobenzene derivatives were investigated by UV/Vis and circular dichroism (CD) spectra and the time-dependent (TD)-DFT method. Experimental results and theoretical analyses indicated that the cyclic configurations exhibited better chiroptical features than the others, and the reverse conformation and difference of dextro-/levo-rotation of azobenzenophanes were detected by comparing linear and cyclic structures, which provides an opportunity for the optical-rotation-controlled “smart” materials systems in future.

A stimuli-responsive amphiphilic copolymer poly(NIPAM_m-b-VBNBI_n), including N-isopropylacrylamide (NIPAM) as a thermoresponsive unit and 1-(4-vinyl benzyl)-2-naphthyl-benzimidazole (VBNBI) as a sensitive fluorophore unit, was designed and synthesized by reversible addition-fragmentation chain transfer polymerization. The aqueous solutions of the copolymers exhibited reversible fluorescent response to pH and temperature. In addition, the copolymers showed aggregation-induced fluorescence enhancement in THF/water mixture. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4459–4466

Well-defined cyclic-polymers (cyclic-PAzoMMAs), bearing side-chain phenylazo naphthalene chromophore, were successfully synthesized by the combination of atom transfer radical polymerization (ATRP) and copper(I)-catalyzed azide/alkyne cycloaddition “click” reaction, as verified by GPC, ¹H NMR, FTIR, and MALDI-TOF mass spectrometry. The cyclic-PAzoMMA showed higher glass transition temperatures than the linear-PAzoMMA with the same molecular weight. Interestingly, the cyclic-PAzoMMA exhibited deeper modulation depth (M.D.) induced by SRG, larger value of the photoinduced birefringence, increased fluorescence emission, and longer fluorescence lifetime in comparison with its linear counterpart.

Two novel and well-defined polymers, poly[6-(5-(diphenylamino)-2-((4-methoxyphenyl)diazenyl)phenoxy)hexyl methacrylate] (PDMMA) and poly[6-(4-((3-ethynylphenyl)diazenyl) phenoxy)hexyl methacrylate] (PDPMMA), which bear triphenylamine (TPA) incorporated to azobenzene either directly (PDMMA) or with an interval (PDPMMA) as pendant groups were successfully prepared via reversible addition-fragmentation chain transfer polymerization technique. The electrochemical behaviors of PDPMMA and PDMMA were investigated by cyclic voltammograms (CV) measurement. The hole mobilities of the polymer films were determined by fitting the J-V (current-voltage) curve into the space-charge-limited current method. The influence of photoisomerization of the azobenzene moiety on the behaviors of fluorescence emission, CV and hole mobilities of these two polymers were studied. The fluorescent emission intensities of these two polymers in CH₂Cl₂ were increased by about 100 times after UV irradiation. The oxidation peak currents (I_OX) of the PDMMA and PDPMMA in CH₂Cl₂ were increased after UV irradiation. The photoisomerization of the azobenzene moiety in PDMMA had significant effect on the electrochemical behavior, compared with that in PDPMMA. The changes of the hole mobility before and after UV irradiation were very small for both polymers. The HOMO energies (E_HOMO, HOMO: the highest occupied molecular orbital) of side chain moieties of TPA incorporated with cis-isomer and trans-isomer of azobenzene in PDMMA and PDPMMA were obtained by theoretical calculation, which are basically consistent with the experimental results. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The well-defined azoindazole-containing homopolymer, poly(6-{6-[(4-dimethylamino) phenylazo]-indazole}-hexyl methacrylate) (PDHMA), and amphiphilic diblock copolymer, poly({6-[6-(4-dimethylamino)phenylazo]-indazole}-hexyl methacrylate)-b-poly(2-(dimethylamino)ethylmethacrylate) (PDHMA_m-b-PDMAEMA_n), were successfully prepared via reversible addition-fragmentation chain transfer polymerization technique. The homopolymer and amphiphilic diblock copolymer in CH₂Cl₂ exhibited intense fluorescence emission accompanied by trans–cis photoisomerization of azoindazole group under UV irradiation. The experiment results indicated that the intense fluorescence emission may be attributed to an inhibition of photoinduced electron transfer of the cis form of azoindazole. On the other hand, the intense fluorescence emission of amphiphilic diblock copolymers in water-tetrahydrofuran mixture was observed, which increased with the volume ratio of water in the mixed solvent. The self-aggregation behaviors of three amphiphilic diblock copolymers were examined by transmission electron microscopy, laser light scattering, and UV–vis spectra. The restriction of intramolecular rotation of the azoindazole groups in aggregates was considered as the main cause of aggregation-induced fluorescence emission. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.