Effect Of The Unfluorinated Component On The Surface Structure Of The Fluorinated Copolymer

The excellent performance of the fluorinated materials was believely due to the enrichmentand the packed array structure of the fluorinated groups. Commercial products are mainly therandom copolymers. In order to achieve the desirable results, we need much more fluorinatedmonomers which may be very expensive. At the same time, to minimize the interfacial freeenergy sometimes, surface reconstruction of the fluorinated polymers may occur within seconds.It is challenging to make up a stable film surface with high enrichment of the fluorine and lowfluorine content.In this paper, polystyene-b-poly(2-perfluorooctylethyl methacrylate)(PS428-b-PFMAn)diblock copolymers and polystyene-b-poly(octadecyl methacrylates)/poly(butylmethacrylates)-b-poly(2-perfluorooctylethyl methacrylate)(PS130-b-PODMA/PBMAm-b-PFMAn)triblock copolymers were synthesized by atom transfer radical polymerization (ATRP). Contactangle goniometry (CA), angle-resolution X-ray photoelectron spectroscopy (XPS), X-raydiffraction(XRD), tensiometry using a Wilhelmy plate(DCA), Sum frequency generationvibrational spectroscopy(SFG) and atom force microscopy(AFM) were empolyed to investigatethe relationshipn between the copolymers structures and surface properties. The conclusions asfollows:(1) PS430-b-PFMAnand PS130-b-PODMA/PBMA-b-PFMAnfluorinated block copolymerswere synthesized by atom transfer radical polymerization (ATRP). FT-IR spectroscopy,1H-NMRspectroscopy, Gel permeation chromatograpy (GPC) and fluorine-element analysis(F-EA) wereempolyed to confirm the composition and the structures of these copolymers.(2) The solvent properties had an effect on the film surface properties. Films of PS-b-PFMAor PS-b-PODMA/PBMA-b-PFMA copolymers casted with benzotrifluoride solution exhibitedbetter excellent surface properties compared with those casted with cyclohexanone and toluenesolutions. The copolymers formed micelles in cyclohexanone and toluene solutions, whileunimers in benzotrifluoride solution. Moreover, when the film was cast-coated film withbenzotrifluoride solution, the perfluoroalkyl side chains would be able to self-assemble into an ordered structure.(3) The PS and PMMA component in copolymer would influence the wettability of theblock copolymers films. Compared to the PS428-b-PFMAnblock copolymer, thePMMA430-b-PFMAmblock copolymer formed more stable micelle in toluene. When they werespin-coated, the mobility of the PFMA segment in PS-b-PFMA film surface was less confinedbecause of the less stable micelle. When they were cast-coated, both the aggregates woulddissociate and the fluorinated moieties would migrate to the surface because of the low surfaceenergy. The difference of the CF3content indicated the PS-b-PFMA form the structure with aless ordered packing because of the stiffness of the benzene.(4) The surface properties of PS130-b-PODMA/PBMAm-b-PFMAncopolymers showedbetter hydrophobicity and oleophobicity than that of the PS130-b-PFMA. The crystallinity of longside alkyl chain of the PODMA could promote the enrichment of the fluorinated moieties, whichalso improved the surface stability when the films were exposed to the polar environment. ThePS and PMMA component would also influence the wettability of the triblock copolymers films.Compared to the PS130-b-PODMA15-b-PFMA6copolymers, the surface of thePMMA230-b-PODMA12-b-PFMA4flims exhibited higher enrichment and better surfaceproperties.(5) The wettability of a liquid crystalline polymer was affected signtificantly by the filmtemperature. When the temperature ranged from25℃to35℃, the modulus and the recedingangle of the PS130-b-PODMA24-b-PFMA6polymer decreased sharply because of the change fromthe smectic phase to the isotropic phase. Meanwhile, the phase of PBMA changed from theglassy to the rubbery. The structure of the perfluoroalkyl side chains became more random due tothe entropy effect resulting in decereasing its receding contact angle.