A third twin: Homopolymers are formed by the copolymerization of two twin monomers. Using the new method of simultaneous twin polymerization, complex hybrid materials can be synthesized in a targeted manner (see scheme), in which, depending upon the combination of twin monomers used, nanostructured hybrid materials with different compositions and properties can be obtained.

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Water-soluble bis(N-acylpiperidone)s with aldehyde-like reactivity are reported to react rapidly with polyvinylamine at room temperature, providing unprecedented clean reaction products. Unlike most amine/ketone reactions that result in arbitrary mixtures of imines, aminals, hemiaminals, or hydrates, in the present study hemiaminals, aminals, or hemiaminal/aminal mixtures are exclusively found. Detailed NMR spectroscopy of solutions, gels, and solids, aided by model reactions, reveals that the hemiaminal/aminal ratio depends on pH, water content, and crosslinking density. Network formation is fully reversible upon changes in pH, with the resulting moduli from rheology spanning almost 3 orders of magnitude. The selfhealing ability of the system is probed by rheology as well, demonstrating maintained material properties of fractured and healed samples. The unusually clean, fast, and reversible chemistry highlights bispiperidones as a class of efficient building blocks with unprecedented possibilities in dynamic covalent chemistry.

We report the synthesis of sterically-stabilized diblock copolymer particles at 20% w/w solids via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of N , N ′-dimethylacrylamide (DMAC) in highly salty media (2.0 M (NH 4 ) 2 SO 4 ). This is achieved by selecting a well-known zwitterionic water-soluble polymer, poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC), to act as the salt-tolerant soluble precursor block. A relatively high degree of polymerization (DP) can be targeted for the salt-insoluble PDMAC block, which leads to the formation of a turbid free-flowing dispersion of PDMAC-core particles by a steric stabilization mechanism. 1 H NMR spectroscopy studies indicate that relatively high DMAC conversions (>99%) can be achieved within a few hours at 30 °C. Aqueous GPC analysis indicates high blocking efficiencies and unimodal molecular weight distributions, although dispersities increase monotonically as higher degrees of polymerization (DPs) are targeted for the PDMAC block. Particle characterization techniques include dynamic light scattering (DLS) and electrophoretic light scattering (ELS) using a state-of-the-art instrument that enables accurate ζ potential measurements in a concentrated salt solution. 1 H NMR spectroscopy studies confirm that dilution of the as-synthesized dispersions using deionized water lowers the background salt concentration and hence causes in situ molecular dissolution of the salt-intolerant PDMAC chains, which leads to a substantial thickening effect and the formation of transparent gels. Thus, this new polymerization-induced self-assembly (PISA) formulation enables high molecular weight water-soluble polymers to be prepared in a highly convenient, low-viscosity form. In principle, such aqueous PISA formulations are highly attractive: there are various commercial applications for high molecular weight water-soluble polymers, while the well-known negative aspects of using a RAFT agent (i.e., its cost, color, and malodor) are minimized when targeting such high DPs.

Poly(vinyl amine) (PVAm) reacts with acetone in aqueous solution. It generates imine and aminal moieties along the PVAm backbone. The molecular structure of acetone‐modified PVAm is confirmed by liquid 1H and 13C as well as solid state 13C NMR and ATR‐FTIR spectroscopies. Model compounds produced from 1,3‐diaminopropane with acetone in chloroform are used to assign the solid state 13C NMR signals of the modified polymer. Quantitative elemental analysis of acetone‐modified PVAm samples supports the analytical results. The mechanism of the imine and aminal formation is discussed with regard to the anomeric stabilization of the incipient hemiaminal intermediate. The rapid and unexpectedly favorable formation of PVAm acetone hemiaminal, acetone imine, and aminal formation has implications for the conduct of PVAm research and even the interpretation of prior published results. As acetone was often used in the past to precipitate waterborne PVAm derivatives, this finding has a severe impact on the interpretation of research results. The consequences and the revised interpretation of selected publications are discussed.