| The morphology of nanocomposite latex particle directly affects film-forming and application properties of emulsion.Janus composite latex particles have the characteristics of special morphologies and anisotropic effects,which make materials new or enhanced properties.This research has become one of the hotspots in composite latex particles.Based on the previous research of the research group,dumbbell-like and snowman-like nano SiO2/polyacrylate?PA?Janus composite emulsion and rod-like SiO2/PA Janus composite emulsion were prepared by one-step miniemulsion polymerization,cross-linking driven phase separation method and self-assembly combined with in-situ polymerization in this study.The influences of Janus structure on film property and application performance were also explored.The specific details were described as follows:Dumbbell-like nano SiO2@styrene-acrylate Janus composite emulsion was prepared by one-step miniemulsion polymerization.When the dosage of azodiisobutyronitrile was 3.5%,the mass ratio of styrene to butyl acrylate was4:6,the dosage of?-methacryloxypropyltrimethoxysilane was 4%,and the dosage of tetraethyl orthosilicate?TEOS?was 6%,the composite emulsion had no gel,high conversion rate and narrow particle size distribution,and had excellent mechanical properties and water resistance.The TEM results showed that morphology of the composite latex particles showed a process from core-shell structure to dumbbell shape with the prolongation of polymerization time.The results of SEM and EDS showed that nano SiO2 dispersed uniformly in the films and some pores appeared in the film.The application results showed that the tear strength,the air permeability and water vapor permeability of leather samples coated with dumbbell-like nano SiO2@styrene-acrylate Janus composite emulsion were increased respectively by more than 13%,80%and 2%compared with pure styrene-acrylate and commercially available PA emulsion.Snowman-like nano SiO2/PA Janus composite emulsions were prepared by cross-linking driven phase separation method.When the content of ammonium persulfate,divinylbenzene and TEOS was 4.5%,5%and was 2%respectively,composite emulsions had high conversion rate,narrow particle size distribution,and excellent water resistance for film.FT-IR results showed that divinylbenzene cross-linked with polyacrylate segments.We compared the properties of snowman-like nano SiO2/PA Janus composite films?Janus C-PA/SiO2?,cross-linking PA films?C-PA?and nano SiO2/PA random composite films?PA/SiO2?.Compared with C-PA and PA/SiO2 films,the tensile strength and water vapor permeability of Janus C-PA/SiO2 films was increased by 142%and7%respectively.And the water resistance of Janus C-PA/SiO2 and C-PA films increased by more than 91%compared with PA/SiO2 films.DSC and TG results showed that the thermal properties of Janus C-PA/SiO2 film were higher than those of the other two films.The AFM results showed that Janus C-PA/SiO2latex particles had a certain self-assembly behavior,forming“twist-like”aggregates in the process of film formation.The application results showed that the air permeability and water vapor permeability of leather samples coated with nano SiO2/PA snowman Janus composite emulsion was increased respectively by more than 91%and 17%compared with leather samples coated commercially available PA emulsion and nano SiO2/PA random composite emulsions.Rod-like SiO2 was prepared by using 4%SDS as structural inducer and 10%TEOS as silicon precursor,and the rod like SiO2/PA Janus composite emulsion was obtained by in-situ growth of PA polymer on the side of the rod-like SiO2.TEM results showed that spherical micelles formed with 1.5%SDS dosage and rod micelles formed with 4%SDS dosage.Compared with spherical SiO2/PA composite latex based film,the tensile strength and water resistance of rod-like SiO2/PA Janus composite latex based film increased by 392.58%and 127.06%respectively.TG results showed that the maximum weight loss temperature of rod-like SiO2/PA Janus composite film was higher than that of spherical SiO2/PA composite film.AFM and SEM results showed that rod-like SiO2 distributed uniformly in the bulk of the films.The application results showed that the tensile strength,elongation at break and tear strength of leather samples coated with rod-like SiO2/PA Janus composite emuslion was increased respectively by more than 14%,23%and 29%compared with leather samples coated commercially available PA emulsion and spherical SiO2/PA composite emulsion.Finally,the film and leather finishing properties of the prepared nano SiO2/PA Janus composite emulsions with different morphologies were compared.The results showed that the mechanical properties of rod-like SiO2/PA Janus composite films were the best,and the water resistances of snowman-like nano SiO2/PA Janus composite films were the best.The application results showed that compared with commercially available PA emulsion coated leather,the tensile strength and tear strength properties of the nano SiO2/PA snowman Janus composite emulsions were better than those of the other two types,which were increased by 19.34%and 20.33%respectively.Moreover,the hygienic property and dry and wet rubbing fastnesses of nano SiO2@styrene-acrylate dumbbell-like Janus composite emulsion coated leather were best. |
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