Abstract
In situ surfactant-free emulsion polymerization can help avoid the utilization of harmful co-solvents and surfactants in the preparation of waterborne poly(urethane-acrylate) (WPUA) nanoemulsion, but the solid content is extremely limited, which will affect the drying rate and film-forming properties. The utilization of polymerizable macrosurfactants can overcome the above problems. However, the research on cationic polymerizable macrosurfactants is extremely scarce. In this work, cationic dimethylaminoethyl methacrylate-b-alkyl methacrylates block copolymers (PDM-b-PRMA) with terminal double bonds and different hydrophobic side chain (HSC) lengths were fabricated via catalytic chain transfer polymerization (CCTP). HSC length of PDM-b-PRMA played an important role in the phase inversion, morphology, rheological behavior of WPUA nanoemulsions, as well as the comprehensive performance of WPUA/PDM-b-PRMA films. Polymerizable PDM-b-PBMA macrosurfactant had smaller molecular weight, lower surface tension and colloidal size than the random copolymer (PDM-co-PBMA) by traditional free radical polymerization. It was easy for PDM-b-PRMA to orientedly assemble at the oil/water interface and provide better emulsifying ability when the carbon number of HSC was four. Compared with WPUA/PDM-co-PBMA, WPUA/PDM-b-PBMA had a smaller particle size, stability and better film-forming properties. This work elucidated the mechanisms of HSC length in the fabrication of cationic PDM-b-PRMA and provides a novel strategy to prepare cationic WPUA of high performance.
Highlights
Due to its outstanding structure designability, waterborne polyurethane (WPU) has been widely applied in several industrial fields [1,2,3,4,5], like coating, sizing agent, and smart surface material, etc. [6,7,8].WPU has several deficiencies, including poor water resistance, low thermal stability, and mechanical properties, which limit the extensive utilization of WPU to some extent [9,10]
The peak at 4.05 ppm could be ascribed to -O-CH2 - in DM unit and the peak at 3.94 ppm is due to the hydrogen of -O-CH2 - in the b-PBMA 14.4 (BMA) unit, proving that BMA monomer was successfully polymerized into the chain of the PDM
The water content at phase inversion point (PIP) decreased to 43% when PDM-b-PBMA was utilized, and the waterborne poly(urethane-acrylate) (WPUA) solid content increased to 40%
Summary
Due to its outstanding structure designability, waterborne polyurethane (WPU) has been widely applied in several industrial fields [1,2,3,4,5], like coating, sizing agent, and smart surface material, etc. [6,7,8]. The investigations on cationic double-bond terminated polymerizable macrosurfactants are scarce, as well as the studies on the utilization of cationic double-bond terminated block-copolymer surfactant for the preparation of cationic WPUA. We first report the preparation of cationic dimethylaminoethyl methacrylate-b-alkyl methacrylates block copolymers (PDM-b-PRMA) with terminal double bonds and different hydrophobic side chain (HSC) length cationic double-bond terminated, as well as its application for the preparation of cationic WPUA colloidal dispersions. Catalytic chain transfer polymerization (CCTP) was adopted to fabricate cationic double-bond terminated block-copolymer surfmer of controlled molecular weight, which has been demonstrated to be an effective approach to prepare double bond terminated block polymer [43,44]. Effects of HSC length in PDM-b-PRMA on the phase inversion behavior and emulsion polymerization of WPUA were investigated, as well as the film performance
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