Preparation and Performance Study of HTPB-g-(PNIPAM/PEG) Thermoresponsive Polymer Brush

In recent years, a great deal of work has been devoted to the development of thermoresponsive polymers that can be made into new types of smart materials. In this paper, a branched polymer, HTPB-g-(PNIPAM/PEG), with polyolefin chain segments as the backbone and having polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) as side chains was synthesized by ATRP and click reactions using N3-HTPB-Br as the macroinitiator. This initiator was designed and synthesized using hydroxyl-terminated polybutadiene (HTPB) as the substrate. The temperature-responsive behavior of the branched polymer was investigated. The lower critical solution temperature (LCST) of the branched polymer was determined by ultraviolet and visible spectrophotometry (UV-vis) and was found to be 35.2 °C. The relationship between the diameter size of micelles and temperature was determined by dynamic light scattering (DLS). It was found that the diameter size changed at 36 °C, which was nearly consistent with the result obtained by UV-vis. The results of the study indicate that HTPB-g-(PNIPAM/PEG) is a temperature-responsive polymer. At room temperature, the polymer can self-assemble into composite micelles, with the main chain as the core and the branched chain as the shell. When the temperature was increased beyond LCST, the polyolefin main chain along with the PNIPAM branched chain assembled to form the nucleus, and the PEG branched chain constituted the shell.

Pickering Interfacial Catalysts with CO2 and Magnetic Dual Response for Fast Recovering in Biphasic Reaction

Pickering interfacial catalysis provides an excellent platform for biphasic reactions, but the separation and recycling of nanocatalysts is a challenge because of high adsorption energy of nanocatalysts at the liquid-liquid interface. In this work, we represent a new type of versatile Pickering emulsion based on magnetic and CO₂-responsive nanohybrids Fe₃O₄@SiO₂@P(TMA-DEA). The smart nanoparticles can stabilize the water-in-oil Pickering emulsion in the biphasic system and achieve the subsequent demulsification by bubbling CO₂ ascribed to their reversible switching surface. In the absence of energy barrier, the nanohybrids can be easily captured in situ by magnetic field in 2 min and showed excellent recyclability. In the Anelli system for alcohol oxidation, the nanocatalyst exhibited threefold enhancement in catalytic efficiency in comparison with an unemulsified two-phase and little loss on activity after five cycles. The conceptually novel dual-responsive system offers a green and energy-saving strategy for effective recycling of the nanocatalyst and intensification of biphasic reaction.

Synthesis of star thermoresponsive amphiphilic block copolymer nano-assemblies and the effect of topology on their thermoresponse

Well-defined multi-arm star thermoresponsive block copolymer nano-assemblies of [poly(N-isopropylacrylamide)-block-polystyrene]_n [(PNIPAM-b-PS)_n] with n = 1, 2, 3 and 4 arms were synthesized by RAFT dispersion polymerization via polymerization-induced self-assembly.

Switchable Oligo(glycidyl ether) Acrylate Bottlebrushes "Grafted-from" Polystyrene Surfaces: A Versatile Strategy toward Functional Cell Culture Substrates

Thermoresponsive brushes based on linear poly(glycidyl ether)s (PGEs) have already shown to be functional coatings for cell sheet fabrication. In here, we introduce a method to functionalize polystyrene (PS) tissue culture substrates with thermoresponsive coatings comprising glycidyl ether-based bottlebrush architectures. Utilizing the UV-induced "grafting-from" approach, thermoresponsive oligo(glycidyl ether) acrylate (OGEA) macromonomers were polymerized from PS substrates under bulk conditions. Applying ellipsometry, water contact angle (CA), and atomic force microscopy (AFM) measurements, we found that OGEA coatings exhibit a complex, gel-like structure comprising nanosized roughness and exhibit a temperature-dependent phase transition in water through the reversible hydration of OGEA bottlebrush side chains. To assess the utility of the coatings as functional substrates for cell sheet fabrication, human dermal fibroblast (HDF) adhesion and detachment were investigated. By adjusting the bottlebrush properties via the grafting procedure and coating structure, we were able to harvest confluent HDF sheets from functionalized PS substrates in a temperature-triggered, controlled manner. As the first report on surface-grafted bottlebrushes comprising thermoresponsive side chains with molecular weight of up to 1 kDa, this study demonstrates the potential of OGEA-based coatings for cell sheet fabrication.

Synthesis of multi-arm star thermo-responsive polymers and topology effects on phase transition

Linear and star thermo-responsive polymers of poly(N-acryloylsarcosine methyl ester) [(PNASME)_n] and poly(N-isopropylacrylamide) [(PNIPAM)_n] with arm number n = 1, 2, 3 and 4 were synthesized following a core-first method via solution RAFT polymerization employing a series of mono- and multi-functional chain transfer agents.

In situ synthesis of thermoresponsive 4-arm star block copolymer nano-assemblies by dispersion RAFT polymerization

Thermoresponsive 4-arm star block copolymer nano-assemblies were synthesized, and their interesting thermoresponse was investigated.