Shanjun Xu

Starch is a natural polymer which possesses many unique properties and some shortcoming simultaneously. Some synthetic polymers are biodegradable and can be tailor-made easily. Therefore, by combining the individual advantages of starch and synthetic polymers, starch-based completely biodegradable polymers (SCBP) are potential for applications in biomedical and environmental fields. Therefore it received great attention and was extensively investigated. In this paper, the structure and characteristics of starch and some synthetic degradable polymers are briefly introduced. Then, the recent progress about the preparation of SCBP via physical blending and chemical modification is reviewed and discussed. At last, some examples have been presented to elucidate that SCBP are promising materials for various applications and their development is a good solution for reducing the consumption of petroleum resources and environmental problem.

Abstract Starch‐poly(vinyl acetate) bioconjugate of controllable composition and structure was generated via a combination of RAFT polymerization and copper‐catalyzed alkene‐azide cycloaddition. Firstly, well‐defined alkyne‐terminated poly(vinyl acetate) (AT‐PVAc) was prepared by RAFT polymerization of vinyl acetate in the presence of an alkyne‐containing chain transfer agent. Secondly, azide‐functionalized starch (SN) was synthesized by the nucleophilic substitution reaction of starch tosylate and sodium azide. Then, the bioconjugate was obtained through the click reaction of AT‐PVAc and SN. FTIR, elemental analysis, and NMR were used to verify the structure of the intermediates and the bioconjugate. GPC measurements showed that the MW of AT‐PVAc linearly depended on the monomer conversion and the polydispersity indexes ranged from 1.09 to 1.28. TEM analysis exhibited the final product was able to self‐assemble into micelles in aqueous medium, which suggested the product was amphiphilic and confirmed the successful conjugation of starch and PVAc once more. The content of starch in the bioconjugate could be 47.8–89.2%, which was able to be tailored by the feeding ratio of SN/AT‐PVAc and the MW of AT‐PVAc.

Reversible addition-fragmentation chain transfer (RAFT) polymerization was adopted to synthesize starch-based conjugates that possessed controllable architecture and properties. Starch-based xanthate agent was prepared and applied as chain transfer agent to conduct the living/controlled polymerization (LCP) of vinyl acetate, which generated tailor-made conjugates of starch and well-defined poly(vinyl acetate) (SVAc). The relevant derivatives, conjugates of starch and chain length-controlled poly(vinyl alcohol) (SVA), were obtained subsequently. Various characterizations such as Fourier transform infrared spectra (FTIR), ultraviolet-visible spectroscopy (UV), proton nuclear magnetic resonance ( 1 H NMR), gel permeation chromatography (GPC), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA) were performed to examine the structure of intermediates and the starch-based conjugates. Static contact angle measurements revealed that the hydrophilic character of starch-based conjugates was tunable. Well-defined SVAc was amphiphilic and it was able to self-assemble into size controllable micelles, which was verified by contact angles, transmission electron microscopy (TEM) and dynamic light scattering (DLS) tests. SVA exhibited much higher capability to form physically cross-linked hydrogel than starch did. Both the characteristic of SVAc and SVA were chain length-dependent.