Gradient Poly(styrene-<i>co</i>-polyglycidol) Grafts via Silicon Surface-Initiated AGET ATRP

Gradient copolymer grafts of styrene and α-<i>tert</i>-butoxy-ω-vinylbenzyl-poly­(glycidol ethoxyethyl ether) (PGLet), a precursor of α-<i>tert</i>-butoxy-ω-vinylbenzyl-polyglycidol macromonomer (PGL), were prepared on silicon wafers via a surface-initiated activator generated by electron transfer radical polymerization (AGET ATRP). Silicon plates with previously attached 2-bromoisobutyrate served as a macroinitiator for the AGET ATRP (activator generated by electron transfer) of styrene and PGLet. The copolymers’ gradient P­(S-<i>co</i>-PPGL) of composition and thickness was obtained by a simple method where the plates were slowly removed from reaction mixture using a step motor. PGLet was added continuously (dropwise) into the reactor during withdrawal of the plates from solution in order to increase the relative concentration of PGLet in polymerization mixture. A range of strategies of making grafts was tested. The plates with copolymers grafts were analyzed by various techniques, like XPS, ellipsometry, and FTIR spectroscopy. The results indicate that the AGET ATRP process is dependent on the styrene/PGLet macromonomer ratio in the polymerization mixture. Under optimal conditions, the addition of PGLet during polymerization and subsequent deprotection of hydroxyl groups of PGLet permit to obtain plates with a novel copolymer layer with composition, thickness, and wettability gradient. Plates with chemical composition of copolymer grafts gradient served as versatile supports with controlled hydrophilic/hydrophobic area and were suitable for tailored deposition of particles

Facile Arm-First Synthesis of Star Block Copolymers via ARGET ATRP with ppm Amounts of Catalyst

Star polymers with block copolymer arms were prepared by atom transfer radical polymerization (ATRP) via an arm-first method. Several macroinitiators based on block copolymers (MIs), PBA-<i>b</i>-P<i>t</i>BA–Br, P<i>t</i>BA-<i>b</i>-PBA–Br, PSAN-<i>b</i>-PBA–Br, and PBA-<i>b</i>-P<i>t</i>BA–Br, were prepared by activators regenerated by electron transfer (ARGET) ATRP to maintain high chain-end functionality. Then the MIs were reacted with divinylbenzene as a cross-linker to form star-shaped polymers via ARGET ATRP. Several parameters including concentration of reducing agent, copper catalyst concentration, degree of polymerization (DP) of MIs, and composition of MIs were investigated. A high level of control was achieved by sequential feeding of the reducing agents for DP_MI ≤ 100. Stars in >95% yield and with narrow molecular weight distributions (<i>M</i>_w/<i>M</i>_n < 1.3) were obtained under the optimized polymerization condition

Preparation of Polymeric Nanoscale Networks from Cylindrical Molecular Bottlebrushes

The design and control of polymeric nanoscale network structures at the molecular level remains a challenging issue. Here we construct a novel type of polymeric nanoscale networks with a unique microporous nanofiber unit employing the intra/interbrush carbonyl cross-linking of polystyrene side chains for well-defined cylindrical polystyrene molecular bottlebrushes. The size of the side chains plays a vital role in the tuning of nanostructure of networks at the molecular level. We also show that the as-prepared polymeric nanoscale networks exhibit high specific adsorption capacity per unit surface area because of the synergistic effect of their unique hierarchical porous structures. Our strategy represents a new avenue for the network unit topology and provides a new application for molecular bottlebrushes in nanotechnology