Hydrophobic films of acrylic emulsion by incorporation of fluorine-based copolymer prepared through the RAFT emulsion copolymerization

Abstract

Abstract In this work, the hydrophobicity of traditional acrylic emulsion films was remarkably improved by introducing some fluorinated diblock copolymer emulsions. Reversible addition-fragmentation chain transfer (RAFT) was utilized to synthesize poly(methacrylic acid)-b-poly(2,2,2-trifluoroethyl methacrylate-co-2,2,3,4,4,4-hexafluorobutyl acrylate) (PMAA-b-P(TFEMA-co-HFBA)) amphiphilic block copolymer emulsion by using the PMAA homopolymer with dithiobenzoate end-groups as macro-RAFT agent. The hydrophobic block of P(TFEMA-co-HFBA) was designed with the various P(TFEMA-co-HFBA) block lengths and p0 ([TFEMA]0/[HFBA]0). And the final conversion of mixed fluorinated monomers (TFEMA, HFBA) could reach about 70% when the value of p0 was greater than 1/2. With the formation of solvophobic P(TFEMA-co-HFBA) block by propagating the fluorinated monomers on the PMAA chain, the PMAA-b-P(TFEMA-co-HFBA) block copolymer in situ self-assembled into core/shell particle with P(TFEMA-co-HFBA) and PMAA blocks as core and shell matrix, respectively. The number-average-particle-diameter of core/shell particles located in the range from 56 to 93 nm was discovered by the way of self-assembly nucleation. The particle size distribution (PSD) of all samples is close to the traditional acrylic emulsion system. The fluorinated block with low surface energy has good hydrophobicity, hence, the traditional acrylic emulsion film modified by the fluorinated diblock copolymer emulsions exhibited excellent hydrophobicity. The effects of various parameters such as the treatment temperature, the processing time, the fluorinated diblock copolymer emulsions ratios and the composition of fluorinated diblock copolymer emulsions on the hydrophobicity of fluorinated composite film were also investigated in this work. The water contact angles of the final fluorinated composite films with water are more than 100° and the fluorinated composite films have good hydrophobicity with low amounts fluoropolymer emulsions (5–20%).