Preparation And Properties Of Cellulose Nanocrystals/Fluorinated Polyacrylate Soap-free Emulsion Base On Pickering Emulsion Polymerization

Cellulose nanocrystal(CNC)not only has a good crystallinity,a large aspect ratio,and a high Young's modulus,but also has biodegradability and biocompatibility,so they are widely used in fields of coatings,composite materials,biomedical and so on.Fluorinated polyacrylate has many excellent properties such as chemical stability,high thermal stability,antifouling and water-oil repellency,and can be used as textile finishing agent to improve water-oil repellency and antifouling properties of textile.CNC can be used as Pickering stabilizer to prepare fluorinated polyacrylate soap-free emulsion.Thus,the negative effects of residual low molecular weight surfactant on the emulsion and film can be overcome.Meanwhile,the water-oil repellency and mechanical properties of film can be improved by introducing the cellulose nanocrystals.In this paper,cellulose nanocrystals/fluorinated polyacrylate emulsion was synthesized via Pickering emulsion polymerization.The main results obtained are as follows.The amphiphilic triblock copolymer PDMAEMA-b-PGMA-b-PHFBA containing epoxy groups in the middle of the chains was first synthesized via RAFT polymerization,and was used in the preparation of PDMAEMA-g-CNC-g-PHFBA by ring-opening reaction between epoxy groups and hydroxyl groups in CNC.The results showed that the PDMAEMA-g-CNC-g-PHFBA could be dispersed in different polar solvents due to its intermediate wettability and amphiphilicity.PDMAEMA-g-CNCg-PHFBA micellar solution contain unimolecular micelle and multi-molecular micelle,and the micelle size decreased with the increase of p H value.The Pickering emulsion was prepared using PDMAEMA-g-CNC-g-PHFBA as Pickering stabilizer.The results showed that the Pickering emulsion had good stability under the conditions that the p H value was 1.07,the volume ratio of oilto water was 3:7,the PDMAEMA-g-CNC-g-PHFBA concentration was 0.1 wt%and the NaCl concentration was 0.1~0.2 wt%,respectively.The volume of emulsion layer and stability of Pickering emulsion decreased with the increase of pH value.And the obtained Pickering emulsion had good long-term stability up to more than three months.In addition,the Pickering emulsion possessed temperature responsive.The cellulose nanocrystals/fluorinated polyacrylate soap-free emulsion was prepared via Pickering emulsion polymerization using PDMAEMA-g-CNC-g-PHFBA as stabilizer.The results showed that the cellulose nanocrystals/fluorinated polyacrylate emulsion and latex film with excellent performances were sythesized under the condition that the stirring speed was 200 r/min,the reaction temperature was 75 ?,the dosage of initiator was 1 wt%,pH value was 2.06,the mass ratio of MMA to BA was 4:6,the PDMAEMA-g-CNC-g-PHFBA concentration was 1.0 wt%,the dosage of HFBA was 10 wt%,respectively.The results of DLS and TEM showed that the latex particles presented as spherical with a narrow distribution.The water-oil repellency and mechanical properties of the film increased with the increase of PDMAEMA-g-CNC-g-PHFBA dosage.The contact angle of the latex films increased firstly and then decreased with the increase of heat treatment temperature.The contact angle of the latex film was the highest when temperature was 95 ?.In the process of Pickering emulsion polymerization,latex particles formed by secondary particle nucleation.The cellulose nanocrystals/fluorinated polyacrylate soap-free emulsion was used for fabric finishing.SEM result showed that a layer of polymer film with low surface energy formed on the surface of fabric.The contact angle of fabric increased with the increase of PDMAEMA-g-CNC-g-PHFBA dosage.The water-oil repellency of fabric was improved,which was the result of combination effect of low surface energy and rough surface.