Porous polymeric films are of paramount importance in many areas of modern science and technology. However, processing methods typically based on direct writing, imprint, and lithography techniques have low throughput and are often limited to specific fabricated shapes. Herein, we demonstrate the directional photomanipulation of breath figure arrays (BFAs) formed by an azobenzene-containing block copolymer to address the aforementioned problems. Under the irradiation of linearly polarized light, the round pores in the BFAs were converted to rectangular, rhombic, and parallelogram-shaped pores in 30 min, due to the anisotropic mass migration based on the photo-reconfiguration of the azobenzene units. Through a secondary irradiation after rotating the sample by 90°, the transformed pores were apparently recovered. Therefore, this non-contacted, directional photomanipulation technique in conjunction with breath figure processing opens a new route to nano/microporous films with finely tuned features.

Porous polymeric films are of paramount importance in many areas of modern science and technology. However, processing methods typically based on direct writing, imprint, and lithography techniques have low throughput and are often limited to specific fabricated shapes. Herein, we demonstrate the directional photomanipulation of breath figure arrays (BFAs) formed by an azobenzene-containing block copolymer to address the aforementioned problems. Under the irradiation of linearly polarized light, the round pores in the BFAs were converted to rectangular, rhombic, and parallelogram-shaped pores in 30 min, due to the anisotropic mass migration based on the photo-reconfiguration of the azobenzene units. Through a secondary irradiation after rotating the sample by 90°, the transformed pores were apparently recovered. Therefore, this non-contacted, directional photomanipulation technique in conjunction with breath figure processing opens a new route to nano/microporous films with finely tuned features.

Well-defined azobenzene-containing side chain liquid crystalline diblock copolymers composed of poly[6-[4-(4-methoxyphenylazo)phenoxy]hexyl methacrylate] (PAzoMA) and poly(glycidyl methacrylate) (PGMA) were synthesized by a two-step reversible addition–fragmentation chain transfer polymerization (RAFT). The thermal liquid-crystalline phase behavior of the PGMA-b-PAzoMA diblock copolymers in bulk were measured by differential scanning calorimetry (DSC) and polarized light microscopy (POM). The synthesized diblock copolymers exhibited a smectic and nematic liquid crystalline phase over a relatively wide temperature range. With increasing the weight fraction of the PAzoMA block, the phase transition temperatures, and corresponding enthalpy changes increased. Atomic force microscope (AFM) measurements confirmed the formation of the microphase separation in PGMA-b-PAzoMA diblock copolymer thin films and the microphase separation became more obvious after cross-linking the PGMA block. The photochemical transition behavior of the PGMA-b-PAzoMA diblock copolymers in solution and in thin films were investigated by UV–vis spectrometry. It was found that the trans–cis isomerization of diblock copolymers was slower than that of the corresponding PAzoMA homopolymer and the photoisomerization rates decreased with increasing either the length of PAzoMA block or PGMA block. The photo-induced isomerization in solid films was quite different with that in CHCl₃ solution due to the aggregation of the azobenzene chromophore. The cross-linking structures severely suppressed the photoisomerization of azobenzene chromophore. These results may provide guidelines for the design of effective photo-responsive anisotropic materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2165–2175, 2013

Well-defined azobenzene-containing side-chain liquid crystalline diblock copolymers composed of poly[6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate] (PMMAZO) and poly(γ-benzyl-L-glutamate) (PBLG) were synthesized by click reaction from alkyne- and azide-functionalized homopolymers. The alkyne-terminated PMMAZO homopolymers were synthesized by copper-mediated atom transfer radical polymerization with a bromine-containing alkyne bifunctional initiator, and the azido-terminated PBLG homopolymers were synthesized by ring-opening polymerization of γ-benzyl-L-glutamate-N-carboxyanhydride in DMF at room temperature using an amine-containing azide initiator. The thermotropic phase behavior of PMMAZO-b-PBLG diblock copolymers in bulk were investigated using differential scanning calorimetry and polarized light microscopy. The PMMAZO-b-PBLG diblock copolymers exhibited a smectic phase and a nematic phase when the weight fraction of PMMAZO block was more than 50%. Photoisomerization behavior of PMMAZO-b-PBLG diblock copolymers and the corresponding PMMAZO homopolymers in solid film and in solution were investigated using UV–vis. In solution, trans–cis isomerization of diblock copolymers was slower than that of the corresponding PMMAZO homopolymers. These results may provide guidelines for the design of effective photoresponsive anisotropic materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

A series of novel amphiphilic brush-dendritic-linear poly[poly(ethylene glycol) methyl ether methacrylate]-b-polyamidoamine-b-poly(ε-caprolactone) copolymers (PPEGMEMA-b-D_m-b-PCL) (m = 1, 2, and 3: the generation number of dendron) were synthesized by the combination techniques of click chemistry, atom transfer radical polymerization (ATRP), and ring-opening polymerization (ROP). The brush-dendritic copolymers bearing hydrophilic brush PPEGMEMA and hydrophobic dendron polyamidoamine protected by the tert-butoxycarbonyl (Boc) groups [D_m-(Boc) (m = 1, 2, and 3)] were for the first time prepared by ATRP of poly(ethylene glycol) methyl ether methacrylate monomer (PEGMEMA) initiated with the dendron initiator, which was prepared from 2′-azidoethyl-2-bromoisobutyrate (AEBIB) and D_m-(Boc) terminated with a clickable alkyne by click chemistry. Then, the brush-dendritic copolymers with primary amine groups (PPEGMEMA-b-D_m) were obtained from the removal of the protected Boc groups of the brush-dendritic copolymers in the presence of trifluoroacetic acid. The brush-dendritic-linear PPEGMEMA-b-D_m-b-PCL copolymers were synthesized from ROP of ε-caprolactone monomer using PPEGMEMA-b-D_m as the macroinitiators and stannous octoate as catalyst in toluene at 130 °C. To the best of our knowledge, this is the first report that integrates hydrophilic brush polymer PPEGMEMA with hydrophobic polyamidoamine (PAMAM) dendron and PCL to form amphiphilic brush-dendritic-linear copolymers. The amphiphilic brush-dendritic-linear copolymers can self-assemble into spherical micellar structures in aqueous solution. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A facile approach is offered to synthesize well-defined amphiphilic ABC triblock copolymers composed of poly(ethylene glycol) monomethyl ether (MPEO) as A block, poly(L-lysine) (PLLys) as B block, and poly(ε-caprolactone) (PCL) as C block by a combination of ring-opening polymerization (ROP) and click reactions. The propargyl-terminated poly(Z-L-lysine)-block-poly(ε-caprolactone) (MPEO-PzLLys-PCL) diblock copolymers were synthesized via the ring-opening polymerization of N^ε-carbobenzoxy-L-lysine N-carboxyanhydride (Z-L-Lys NCA) in DMF at room temperature using propargyl amine as an initiator and the resulting amino-terminated poly(Z-L-lysine) then used in situ as a macroinitiator for the polymerization of ε-caprolactone in the presence of stannous octoate as a catalyst. The triblock copolymers poly(ethylene glycol) monomethyl ether –block-poly(Z-L-lysine)-block-poly(ε-caprolactone) (MPEO-PzLLys-PCL) were synthesized via the click reaction of the propargyl-terminated PzLLys-PCL and azido-terminated poly(ethylene glycol) monomethyl ether (PEO-N₃) in the presence of CuBr and 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) catalyst system. After the removal of Z groups of L-lysine units, amphiphilic and biocompatible ABC triblock copolymers MPEO-PLLys-PCL were obtained. The structural characteristics of these ABC triblock copolymers and corresponding precursors were characterized by NMR, IR, and GPC. These results showed the click reaction was highly effective. Therefore, a facile approach is offered to synthesize amphiphilic and biocompatible ABC triblock copolymers consisting of polyether, polypeptide and polyester. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Well-defined asymmetric amphiphilic ABA′ block copolymers composed of poly(ethylene oxide) monomethylene ether (MPEO) with different molecular weights as A or A′ block and poly(styrene) (PS) as B block were synthesized by the combination of atom transfer radical polymerization (ATRP) and click reactions. First, bromine-terminated diblock copolymer poly(ethylene oxide) monomethylene ether-block-poly(styrene) (MPEO-PS-Br) was prepared by ATRP of styrene initiated with macroinitiator MPEO-Br, which was prepared from the esterification of MPEO and 2-bromoisobutyryl bromide. Then, the azido-terminated diblock copolymers MPEO-PS-N₃ were prepared through the bromine substitution reaction with sodium azide. Propargyl-terminated MPEO with a different molecular weight was prepared under the basic condition from propargyl alcohol and p-toluenesulfonyl-terminated MPEO, which was prepared through the esterification of MPEO and p-toluenesulfochloride using pyridine as solvent. Asymmetric amphiphilic ABA′ block copolymers, with a wide range of number–average molecular weights from 1.92 × 10⁴ to 2.47 × 10⁴ and a narrow polydispersity from 1.03 to 1.05, were synthesized via a click reaction of the azido-terminated diblock copolymers and the propargyl-terminated MPEO in the presence of CuBr and 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) catalyst system. The structures of these ABA′ block copolymers and corresponding precursors were characterized by NMR, IR, and GPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

A series of novel side-chain liquid crystalline ABC triblock copolymers composed of poly(ethylene oxide) (PEO), polystyrene (PS), and poly[6-(4-methoxy-4′-oxy-azobenzene) hexyl methacrylate] (PMMAZO) were synthesized by atom transfer radical polymerization (ATRP) using CuBr/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) as a catalyst system. First, the bromine-terminated diblock copolymer poly(ethylene oxide)-block-polystyrene (PEO-PS-Br) was prepared by the ATRP of styrene initiated with the macro-initiator PEO-Br, which was obtained from the esterification of PEO and 2-bromo-2-methylpropionyl bromide. An azobenzene-containing block of PMMAZO with different molecular weights was then introduced into the diblock copolymer by a second ATRP to synthesize the novel side-chain liquid crystalline ABC triblock copolymer poly(ethylene oxide)-block-polystyrene-block-poly[6-(4-methoxy-4′-oxy-azobenzene) hexyl methacrylate] (PEO-PS-PMMAZO). These block copolymers were characterized using proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatograph (GPC). Their thermotropic phase behaviors were investigated using differential scanning calorimetry (DSC) and polarized optical microscope (POM). These triblock copolymers exhibited a smectic phase and a nematic phase over a relatively wide temperature range. At the same time, the photoresponsive properties of these triblock copolymers in chloroform solution were preliminarily studied. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4442–4450, 2008