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Poly(L‐lactide) (PLLA) on poly(2‐hydroxyethyl methacrylate) (PHEMA) backbone was prepared by a combination of atom transfer radical polymerization (ATRP) and ring‐opening polymerization (ROP). The structure of the comb polymer was analyzed by wide angle X‐ray diffraction (WAXD), small angle X‐ray scattering (SAXS), and differential scanning calorimetry (DSC). WAXD result indicates that the comb polymer has α crystalline modification with a 103 helical conformation. Lamellar parameters of the crystalline structure were obtained by one‐dimension correlation function (1DCF) calculated from SAXS results. The calculations show that the thickness of crystalline layer is controlled by annealing temperature and comb structure. DSC was applied to study kinetics of the crystallization and melting behavior. Two melting peaks on melting curves of the comb polymer at different crystallization temperature were detected, and the peak at higher temperature is attributed to the melt‐recrystallization. The equilibrium melting temperature is found to be influenced by the comb structure. In this article the effects of the comb structure on Avrami exponent, equilibrium melting point and melting peak of the comb polymer were discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 589–598, 2008

Polystyrene (PS) and poly(methyl methacrylate) (PMMA) mixed polymer brushes on the surface of clay layers were prepared by using in situ free radical polymerization. Free radical initiator molecules with two quaternary ammonium groups at both ends were intercalated into the interlayer spacing of clay layers. The amount of polymer brushes grafted on the surface of clay layers can be controlled by controlling the polymerization time. Thermogravimetric analysis, X-ray diffraction, and high-resolution transmission electron microscope results indicated successful preparation of the mixed polymer brushes on the surface of clay layers. The kinetics of the grafting of the monomers was also studied. The mixed polymer brushes on the surface of clay layers were used as compatibilizers in blends of PS and PMMA. In the blends, the intercalated clay particles tend to locate at the interface of two phases reducing the interfacial tension. In the meanwhile, PMMA homopolymer chains tend to intercalate into clay layers. The driving force for the intercalation is the compatibility between homo-PMMA chains and PMMA brushes on the surface of clay layers.

An amphiphilic asymmetric comb polymer with pendant pyrene groups and poly(N-isopropylacrylamide) (PNIPAM) side chains was synthesized based on click chemistry and reversible addition-fragmentation chain transfer polymerization. Gel permeation chromatography, FTIR, and (1)H NMR results all indicated successful synthesis of a well-defined comb polymer. The photophysical properties and self-assembly of the polymer in solution were studied by UV-vis spectroscopy, fluorescence technique, and transmission electron microscopy. The intensity ratio of the excimer peak (I(E)) to the monomer peak (I(M)) of the comb polymer in THF was used to monitor the formation of inter- or intramolecular excimers. At low polymer concentration, the value of I(E)/I(M) kept unchanged, indicating the formation of intramolecular excimer; at high polymer concentration, the value increased rapidly with concentration because of the formation of intermolecular excimer. The change of the intensity ratio of the first to the third vibronic band (I(1)/I(3)) on the monomer emission of the comb polymer also proved the association of the pendant pyrene groups in THF at high polymer concentration. In aqueous solution, the comb polymer chains self-assembled into vesicles with pyrene groups in the walls and PNIPAM side chains in the coronae. The value of the critical aggregation concentration of the polymer was determined by fluorescence technique. Temperature exerted a significant effect on the size and morphology of the vesicles. At a temperature above the lower critical solution temperature (LCST) of PNIPAM, PNIPAM brushes in the coronae of vesicles collapsed on the surface of the structures forming nanosized domains, and vesicles with smaller size were obtained. Fluorescence quenching experiments indicated that the collapsed PNIPAM chains protected a part of pyrene groups from being quenched by nitromethane at a temperature above the LCST of PNIPAM.