Vinyl sulfone-substituted L-cysteine N-carboxyanhydride (VSCys-NCA) monomer was designed and developed to afford a novel and versatile family of vinyl sulfone (VS)-functionalized polypeptides, which further offer a facile access to functional polypeptide-based materials including glycopolypeptides, functional polypeptide coatings, and in situ forming polypeptide hydrogels through Michaeltype addition chemistry under mild conditions. VSCys-NCA was obtained in two straightforward steps with a high overall yield of 76%. The copolymerization of γ-benzyl L-glutamate NCA (BLG-NCA), N-benzyloxycarbonyl-L-lysine NCA (ZLL-NCA), or L-leucine NCA (Leu-NCA) with VSCys-NCA using 1,1,1-trimethyl-N-2-propenylsilanamine (TMPS) as an initiator proceeded smoothly in DMF at 40°C, yielding P(BLG-coVSCys), P(ZLL-co-VSCys), or P(Leu-co-VSCys) with defined functionalities, controlled molecular weights, and moderate polydispersities (PDI = 1.15−1.50). The acidic deprotection of P(BLG-co-VSCys) and P(ZLL-co-VSCys) furnished water-soluble VS-functionalized poly(L-glutamic acid) (P(Glu-co-VSCys)) and VS-functionalized poly(L-lysine) (P(LL-co-VSCys)), respectively. These VS-functionalized polypeptides were amenable to direct, efficient, and selective postpolymerization modification with varying thiol-containing molecules such as 2-mercaptoethanol, 2-mercaptoethylamine hydrochloride, L-cysteine, and thiolated galactose providing functional polypeptides containing pendant hydroxyl, amine, amino acid, and saccharide, respectively. The contact angle and fluorescence measurements indicated that polymer coatings based on P(Leu-coVSCys) allowed direct functionalization with thiol-containing molecules under aqueous conditions. Moreover, hydrogels formed in situ upon mixing aqueous solutions of P(Glu-co-VSCys) and thiolated glycol chitosan at 37°C. These vinyl sulfonefunctionalized polypeptides have opened a new avenue to a broad range of advanced polypeptide-based materials. ■ INTRODUCTIONSynthetic polypeptides inherit many intriguing properties of proteins such as excellent biocompatibility, biodegradability, unique hierarchical assembly property, versatile structures and functionalities, and biological activity. 1−4 They have been widely used as biomimetic materials, 5−7 drug nanocarriers, 8−15 tissue engineering scaffolds, 16−18 and potent catalysts. 19,20 The ring-opening polymerization (ROP) of N-carboxyanhydride (NCA) is the most viable strategy for the large-scale synthesis of high molecular weight (MW) polypeptides. 21 In particular, the recent development of controlled NCA polymerization techniques e.g. using transition metal complexes, 22 amine hydrochloride, 23 amine under high vacuum, 24 amine under low temperature, 25 or silazane derivatives 26 renders it possible to prepare polypeptides with controlled MWs and low polydispersities.The emerging biomedical technology demands advancement of functional biomaterials. 27−29 Functional polypeptides containing e.g. carboxylic acid, amine, hydroxyl, and saccharide groups have been obtained by ...

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The mechanical loading induced flow of glassy polymers is triggered by the nucleation of shear transformation units, and strongly depends on the initial microstructural state of the material. Therefore, investigation of the possible relationship between the microstructural state variables and plastic deformation is required for a better understanding of the macroscopic response of this class of materials during large deformation. In this study, free volume content is considered as a state variable and thermal treatment is selected as a process through which the accelerated and forced evolution of the free volume can be imposed. For two well-known glassy polymers, poly(methyl methacrylate) and polycarbonate, the free volume content alteration upon annealing is monitored via positron annihilation spectroscopy, and the changes of the micro-and macromechanical properties are also obtained by utilizing nanoindentation technique and employing the homogeneous amorphous flow theory. The correlation between the microstructural state variable, that is, free volume, and the micromechanical state variable, that is, shear activation volume, is then investigated. The results reveal opposite direction of alterations of free volume and shear activation volume with annealing temperature. Accordingly, the possibility of the existence of an interrelation between these two state variables is critically discussed.

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