Controlled Graft Polymerization Of Vinyl Monomer On The Cellulose Via HRP-initiated RAFT Polymerization

Graft polymerization modification of materials by oxidative reductase catalysis has gained a large number of achievements.However,like traditional free radical polymerization,the enzyme-initiated free radical polymerization process is difficult to control,and the graft polymer chain on the materials has a wide molecular weight distribution,resulting in poor performance of the modified materials.In this study,RAFT chain transfer agent was immobilized on the surface of the cellulose materials,and then RAFT graft polymerization was initiated by enzyme on the surfaces of the materials to control the reaction process and product structure.2-?Dodecylthiocarbonothioylthio?-2-methylpropionic acid?DDMAT?was used as the RAFT chain transfer agent.Firstly,DDMAT was grafted onto the cellulose macromolecule via esterification between the carboxyl group of DDMAT and the hydroxyl group on the cellulose.And then the HRP/ACAC/H₂O₂ ternary system was used to initiate RAFT graft polymerization on the surfaces of the cellulose materials.First,the study investigated the RAFT self-polymerization of vinyl monomers initiated by HRP/ACAC/H₂O₂ system.The molecular weight and polymer dispersity index?PDI?of the polymerization product were measured by GPC,and the influence of DDMAT on the polymerization product was studied.The results showed that the molecular weight distribution of the product had become narrow,and PDI was less than2.In this paper,dextran was used as a cellulose model compound to simulate cellulose graft polymerization under homogeneous conditions.The structure of graft polymerization product was characterized by MALDI-TOF MS and FTIR.The molecular weight of the product indicated that the product might be graft copolymer of dextran and acrylamide.The results of FTIR showed that the characteristic absorption peak of the graft copolymer can be observed in the spectrum,such as C=O and N-H.Then,the study investigated the enzyme-initiated RAFT graft polymerization of vinyl monomers on the different cellulose materials?filter paper,cellulose film,cotton fabric?.The effects of the reaction conditions on the grafting of DDMAT on filter paper were investigated by the ester group content and the degree of hydroxyl substitution of the product.The results showed that the amount of DDMAT,reaction time and reaction temperature had a great influence on the reaction.When the dosage of DDMAT was0.03 g,the reaction time was 32 h,and the reaction temperature was 25°C,a good reaction effect was obtained.The ester content of the product exceeded 1.1 mmol/g.The esterification reaction of dissolved cellulose with DDMAT was carried out,a higher ester group content?1.9 mmol/g?of the product can be obtained.The ATR-FTIR and XPS results of the modified cellulose materials showed that DDMAT was successfully grafted onto the cellulose materials?filter paper,cellulose film,cotton?,and FTIR of DDMAT-cellulose showed a significant increase at 1738 cm^-1.The content of S element on the surface of the cellulose materials was increased after DDMAT graft.The content of N element on the surface of the cellulose materials was increased after graft polymerization of acrylamide.The effect of DDMAT on the reaction process was investigated by the effect of reaction time on the grafting ratio and the monomer conversion.During the graft polymerization of acrylamide,the grafting rate and monomer conversion rate increased linearly with time.The correlation coefficient R²of the fitted straight line was 0.92622 and 0.96702,respectively.The pseudo-first-order kinetic of graft polymerization was y=0.28733x-0.03643?R²=0.94329?;the above results indicated that the graft polymerization was controllable and conforms to the RAFT polymerization.The properties of the cellulose materials after graft polymerization were change.After the cellulose materials were esterified with DDMAT,the materials were changed from hydrophilic to hydrophobic.When further RAFT graft polymerization occurs,the wettability of the products was different.After graft polymerization of acrylamide,the cellulosic materials were hydrophilicity.After graft polymerization of methyl acrylate,the hydrophobic property of the materials was further improved.