Triblock copolymer, PEG-b-PDMAEMA-b-PPy, has been shown as an ideal carrier with remarkable siRNA condensation, high stability, efficient gene release, and negligible cytotoxicity for gene delivery.

A new multicomponent reaction involving 2-hydroxybenzaldehyde, amine, and 2-mercaptobenzaldehyde (HAM reaction) has been developed and applied to multicomponent polymerization and controlled radical polymerization for the construction of random and block copolymers. This chemistry features mild reaction conditions, high yield, simple isolation, and water as the only byproduct. With the advantages of the distinct nucleophilicity of thiol and hydroxyl groups, the chemistry could be used for stepwise labeling and modifications on primary amines. The Janus chemical joint formed from this reaction exhibits degradability in buffers and generates the corresponding starting reagents, allowing amine release. Interestingly, the chemical joint exhibits thermally activated reversibility with water as the catalyst. This multicomponent dynamic covalent feature has been applied to the metamorphosis of random and block copolymers, generating polymers with diverse architectures. This chemistry is expected to be broadly applicable to synthetic polymer chemistry and materials science.

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The block copolymers of poly(acrylic acid)-bpoly(vinyl alcohol) (PAA-b-PVA) were obtained from the hydrolysis of poly(methyl acrylate)-b-poly(vinyl acetate) (PMA-b-PVAc), which was synthesized by cobalt-mediated radical polymerization (CMRP) using the cobalt(II) porphyrin complex (Co II (TMP)) as the mediator. The mechanical properties of the PAA-b-PVA free-standing films could be tuned by the pH of the aqueous solution used to cast the films. The block copolymer films showed a much higher tensile strain and fractural tensile strength than the films prepared from the blends of PAA and PVA homopolymers. FTIR and morphological characterizations suggested that the tensile properties of the films were governed by both the hydrogen bonding between PVA and PAA that led to interpolymer complexation and the phase-separated morphology. For a given type of material, the greater extent of interpolymer complexation attained at lower solution pH led to the film with better tensile properties. The difference in the length scale of phase separation was responsible for the large difference in the tensile properties between block copolymer and blend films, where the characteristic nanostructure formed in the block copolymer prescribed a considerably larger amount of interface which enhanced the tensile properties significantly.

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