Highly Stretchable Free-Standing Poly(acrylic acid)-block-poly(vinyl alcohol) Films Obtained from Cobalt-Mediated Radical Polymerization

Abstract

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.

Skin-like hydrogel devices for wearable sensing, soft robotics and beyond

“…showed that the swelling of a PVA−PAA-coated quartz crystal microbalance pH sensor had a short response time of 500 ms, a shrinking time of 800 ms, and sensitivity of 13.2 kHz/pH, in the pH range of 3–10 ( Richter et al., 2004 ). In addition, the PVA−PAA hydrogel is highly stretchable ( Wang et al., 2017 ), which could be useful for wearable and stretchable pH sensors.…”

Straightforward Synthesis of Well-Defined Poly(vinylidene fluoride) and Its Block Copolymers by Cobalt-Mediated Radical Polymerization

“…The third method deals with OMRP, in which a transition-metal complex reversibly traps the propagating polymer radicals. , This strategy has been successfully employed for the radical (co)­polymerization of less reactive monomers, including vinyl acetate (VAc) − , VAc-ethylene, 2-methylene-1,3-dioxepane, and methyl acrylate, with Co II (acac) 2 (acac = acetylacetonate) or bis­(2-formylphenolato)­cobalt­(II) as controlling agent. We have recently reported the first OMRP of VDF under mild experimental conditions, using [R 0 (VAc) ∼4 Co III (acac) 2 ] as initiator (R 0 = primary radical generated by V-70) .…”

Recent advances in CoSalen-catalyzed radical reactions

“…2018年Komeyama等 [55] 报道了CoSalen/Ni催化的卤代 PMA-b-PVAc的合成及其水解制备聚丙烯酸-b-聚乙烯 醇的应用 [58] . 2015年, Debuigne和Determbleur等 CoSalen介导LRP中的配体效应是化学家们十分 关心的问题.…”