Multicompartmental Janus Microbeads from Branched Polymers by Single-Emulsion Droplet Microfluidics

We describe a versatile and facile route for the preparation of Janus microbeads using single emulsion droplet-based microfluidics, in which water droplets that contain a mixture of branched poly­(<i>N</i>-isopropylacrylamide)-<i>co</i>-(poly­(ethylene glycol)­diacrylate)-<i>co</i>-(methacrylic acid) and colloidal particles form the basis of our approach. The colloidal particles, poly­(methyl methacrylate) microspheres or titanium dioxide particles, and iron oxide nanoparticles are spatially positioned within the water droplets through gravity and an externally applied magnetic force, respectively. Evaporation of water leads to gel formation of the branched copolymer matrix as a result of physical cross-linking through hydrogen bond interactions, fixing the spatial position of the colloidal particles. The thermo- and pH-responsive nature of the branched poly­(<i>N</i>-isopropylacrylamide) (PNIPAm)-based copolymer allows for the disintegration of the polymer network of the Janus microbeads and a triggered release of the colloidal content at temperatures below the lower critical solution temperature (LCST) and at increased pH values

Sequence-Controlled Methacrylic Multiblock Copolymers: Expanding the Scope of Sulfur-Free RAFT

Sulfur-free reversible addition–fragmentation transfer polymerization (SF-RAFT) in emulsion allows access to the synthesis of sequence-controlled methacrylic multiblock copolymers. Herein, we expand the scope of SF-RAFT emulsion polymerization by utilizing four different macrochain transfer agents (mCTA) to mediate the synthesis of diblocks and sequence-controlled methacrylic multiblock copolymers. Poly­(methyl methacrylate) (pMMA), poly­(butyl methacrylate) (pBMA), poly­(ethyl methacrylate) (pEMA), and poly­(benzyl methacrylate) (pBzMA) of a similar <i>M</i>_n (∼4300 g mol^–1) were successfully synthesized via catalytic chain transfer polymerization (CCTP) in emulsion. The capability of these mCTAs to act as macroinitiators was investigated through the synthesis of “<i>in situ</i>” diblock copolymers and was then expanded to the synthesis of deca- and hexablock multiblock copolymers with varying degrees of polymerization (DP_n = 10–50 per block, <i>M</i>_n,total = 7000–55 000 g mol^–1), yielding well-defined copolymers with controlled molecular weights, quantitative conversions (>99%), and low dispersities (<i>Đ</i> ∼ 1.2) without employing sulfur or transition metal reagents

An evaluation of supported employment initiatives for disabled people

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