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Abstract: Hyperbranched-linear star block copolymers, hyperbranched poly(siloxysilane)-block-polystyrene (HBPS-b-PSt), were prepared by atom transfer radical polymerization (ATRP) of styrene in xylene, using bromoester-terminated HBPS (HBPS-Br (P3), M n =7500, M w/M n =1.76) as a macroinitiator. The number-average molecular weights of the obtained polymers (M n) were in the range of 21,800–60,000 and molecular weight distributions were unimodal throughout the reaction (M w/M n =1.28–1.40). These polymers showed 5wt.% decomposition temperature (T d5) over 300°C. The DSC thermograms of the resulting polymers indicated two glass transition temperatures (T g). The T g of HBPS segment shifted to higher value while the T g of PSt segment shifted to lower value compared with those of the homopolymers. Preliminary physical characterization related to the solution viscosity of the resulting block copolymers is also reported. [Copyright &y& Elsevier]

Abstract: Hyperbranched polysiloxysilane (HBPS) terminated by the vinyl functional group was synthesized by the self polymerization of AB2 monomer, 1,5-divinyl-1,1,3,5,5-pentamethyltrisiloxane, in the presence of the platinum catalyst. The terminal vinyl group was converted to 2-hydroxyethyl by the reaction with 9-BBN as the hydroboration reagent. The terminal function was then modified to the 2-bromoisobutyryl group by the reaction of hydroxyl group with 2-bromoisobutyryl bromide. The obtained HBPS possessing the 2-bromoisobutyryl terminal group was immobilized on the silica surface by mixing the silica bead and HBPS in hexane. Block copolymer of HBPS and poly(N-isopropylacrylamide) (PIPAAm) was synthesized by the atom transfer radical polymerization (ATRP) using 2-bromoisobutyryl terminated HBPS as a macroinitiator. The molecular weight of the block copolymer was M n=23,500 and M w/M n=1.31. Graft polymerization of N-isopropylacrylamide on the silica surface was carried out on the 2-bromoisobutyryl terminated HBPS immobilized silica bead using ATRP. The PIPAAm grafted silica bead was applied to the column packed material for temperature-responsive HPLC. Two kinds of steroids, hydrophilic and hydrophobic, were successfully separated by the HPLC system. [Copyright &y& Elsevier]

Aromatic hyperbranched polymers, such as hyperbranched poly(ether sulfone), are promising catalytic materials, but the advantages of the hyperbranched structure have not been well understood. In this study, hyperbranched poly(ether sulfone), functionalized with sulfonic acid terminal groups (HBSPES) and its linear analogue (LSPES), were studied as acid catalysts for a model reaction, namely, the esterification of 1-butanol and acetic acid. In the homogeneous catalytic reaction, HBSPES showed a clear advantage in the apparent turnover frequency (TOF). To utilize these polymers as heterogeneous catalysts, they were immobilized onto carbon black (CB) to obtain HBSPES/CB and LSPES/CB. The polymer loading after immobilization was higher with HBSPES/CB, probably due to the dense architecture of the hyperbranched polymer. In the heterogeneous catalytic reaction, HBSPES/CB exhibited a much better catalytic performance than LSPES/CB, possibly benefiting from the good affinity of the hyperbranched polymer to the reaction solution. These experimental observations suggest that aromatic hyperbranched polymers are suitable for use as catalysts. [ABSTRACT FROM AUTHOR]

This study focuses on a copolymer of hyperbranched polystyrene and poly( N -isopropylacrylamide) (HBPSt- g -PNIPAM) as a surface modifier for conventional polystyrene (PSt) dishes to fabricate a thermo-responsive cell culture substrate, and especially discuss the role of the hyperbranched structure on the cell sheet detachment performance. HBPSt- g -PNIPAM was synthesized by grafting PNIPAM from the termini of HBPSt, and cast onto a commercial PSt-dish. Mouse 3T3 fibroblast cells cultivated on the prepared dish were successfully collected as a sheet form after cooling down the dish to 20 °C; however, its linear analogue did not detach cell sheets under the same condition. To highlight the effect of the hyperbranched structure, Langmuir-Blodgett (LB) films of the copolymers were studied. The LB film accumulation experiments suggest that the hyperbranched structure contributes to the exposure of the PSt segment, which probably enhance the immobilization of the PSt segment onto the PSt-dish. [ABSTRACT FROM AUTHOR]

This paper describes the preparation of hyperbranched polystyrene- g -poly( N -isopropylacrylamide) (HBPSt- g -PNIPAM) and its application as a novel thermo-responsive material for cell sheet preparation. HBPSt- g -PNIPAM was synthesized by grafting PNIPAM from the termini of HBPSt via reversible addition fragmentation transfer polymerization. The resulting HBPSt- g -PNIPAM was cast from a solution onto a commercial polystyrene-based dish (PS-dish) to make a thermo-responsive surface for cell cultivation (P4/PS-dish). Mouse 3T3 fibroblast cells were seeded on the P4/PS-dish with 2.5–3.5 μg/cm 2 of PNIPAM and cultured at 37 °C for four days to achieve high confluency. Fairly large cell sheets were successfully collected by cooling the dish to 20 °C. The current material avoids the use of electron beam polymerization, which requires complicated equipment, for fabricating a thermo-responsive surface because PNIPAM is immobilized by the affinity between the hyperbranched polystyrene segment and the PS-dish. [ABSTRACT FROM AUTHOR]

Abstract: Hyperbranched poly(ether sulfone) polymers having sulfonyl chloride end-groups is blended at up to 30w% with linear poly(ether ether ether sulfone)s and a two-phase system is generated via spinodal decomposition upon drying from a DMAc solution. Conversion of the end-groups from sulfonyl chloride to sulfonic acid is accomplished using 16M H2SO4 that is also believed to introduce additional sulfonic acid groups at the interface of the linear polymer. The blend films before and after conversion to sulfonic acid have similar tensile strengths as films composed of solely linear polymer (yield stress >40MPa and Young''s modulus >3GPam). These films are designed to test the viability of hyperbranched polymers as fuel cell membranes. Proton conductivities of up to 0.03Scm−1 are observed at 80°C and 90% R.H indicating a good potential for use of hyperbranched polymers as a proton conduction material. [Copyright &y& Elsevier]