End-functional styrene-maleic anhydride copolymers via catalytic chain transfer polymerization

Styrene-maleic anhydride copolymers have been successfully synthesized using catalytic chain transfer polymerization employing the low spin [bis(difluoroboryl)dimethylglyoximato]cobalt(II) (COBF) complex. By partially replacing styrene with α-methylstyr

Amphiphilic glycosylated block copolypeptides as macromolecular surfactants in the emulsion polymerization of styrene

Diblock copolymers consisting of poly(L-phenyl alanine) and poly(benzyl-L-glutamate) or poly(CBZ-L-lysine), respectively, were synthesized via sequential NCA polymerization. After deprotection, subsequent partial glycosylation of the glutamic acid and lysine units with galactosamine hydrochloride or lactobionic acid yielded amphiphilic block copolypeptides. Moreover, a triblock copolymer poly(L-phenyl alanine-b-L-benzyl glutamate-b-propargylglycine) was obtained and glycosylated by ‘click’ chemistry. Glycosylated block copolypeptides showed improved water solubility and circular dichroism (CD) confirmed the pH dependence of the helix-coil transition. The block copolypeptides were found to be efficient stabilizers in the emulsion polymerization of styrene offering a facile method for the synthesis of polystyrene nanoparticles in the range of 100–140 nm depending on the block copolymer composition and emulsion concentration. This establishes an example of functional polymer additives fully based on renewable building blocks in nanomaterial synthesis. Graphical abstract: Amphiphilic glycosylated block copolypeptides as macromolecular surfactants in the emulsion polymerization of styren

Fractography of poly(N-isopropylacrylamide) hydrogel networks crosslinked with mechanofluorophores using confocal laser scanning microscopy

Due to their soft and brittle nature, the mechanical characterization of polymer hydrogels is a difficult task employing traditional testing equipment. Here, we endowed poly(N-isopropyl acrylamide) (PNIPAAm) hydrogel networks with Diels–Alder adducts of π-extended anthracenes as mechanofluorophore crosslinkers. After swelling the networks with varying amounts of water and subjecting them to force, we visualized the subsequent fluorescence caused by covalent bond scission with confocal laser scanning microscopy (CLSM) and related the intensities to the macroscopic fracture mechanics and the elastic moduli recorded with traditional uniaxial compression. The sensitivity of the mechanofluorophores allowed the analysis of low levels of mechanical stress produced via a hand-induced needle-puncturing process and, thus, is an alternative to conventional force application methods. The detection and precise localization of covalent bond scission via CLSM helps elucidating the interrelationship between molecular structure and the macroscopic properties of chemically crosslinked polymeric hydrogels. We believe that this micro-scale mechanophore-assisted fractography can establish a new paradigm for the mechanical analysis of soft matter in fields covering traditional polymer and life sciences