Synthesis And Surface Properties Of Block Copolymers With Low Content Of Fluorosilicones

Fluorinated polysiloxane (or fluorosilicone) exhibits the properties of waterresistance and solvent resistance as that of fluoropolymers owing to the incorporationof fluorinated alkyl chains. As a copolymer component, fluorinated polysiloxane canimprove the water resistance and solvent resistance of polyacrylate materials. Andelectrospun films with superoleophobic and oil resistance properties are expected tobe obtained via the polymer electrospinning techniques.In this work, firstly, a series of well-defined poly[methyl(3,3,3-tri-fluoropropyl)siloxane]-b-poly(methyl methacrylate)(PMTFPS-b-PMMA) diblock copolymerswere obtained via atom transfer radical polymerization (ATRP). Secondly, theelectrospun films with low contents of fluorosilicone segments, which showedsuper-hydrophobic and solvent resistance properties, was obtained by the way ofelectrospinning. The main results were described as follows:1. The PMTFPS-b-PMMA block copolymers with controlled structure wassynthesized via ATRP reaction, and the kinetics was investigated.The ATRP macro-initiator of fluorosilicone (PMTFPS-Br) was successfullysynthesized by anion ring-opening polymerization of1,3,5-trimethyl-1,3,5-trifluoropropyl)cyclotrisiloxane (F3) and the functionalizationreaction of end groups. Then, PMTFPS-b-PMMA block copolymers with narrowmolecular weight distribution was synthesized via ATRP using CuBr/HMTETA as thecatalytic system under the condition of the removal of water and oxygen. The ATRPof MMA initiated by PMTFPS-Br was proved as a living polymerization via thekinetic study.2. The surface microstructure and properties of the thin films ofPMTFPS-b-PMMA diblock copolymer were investigated in this work. (1) AFM results showed that the surface morphology of PMTFPS-b-PMMAwould be different when the segment ratio was different, and the surface morphologyof films appear some roughness.(2) The results of contact angle meaurements showed that the surface energy ofthe films was between22.07mJ/m2and25.28mJ/m2depending on the content offluorosilicone in PMTFPS-b-PMMA diblock copolymers. The results also indicatethat little content of fluorosilicone segments can improve the water repellency of theblock copolymer surface and reduce the surface energy of block copolymerefficiently.3. The electrospun films of PMTFPS-b-PMMA block copolymer withsuper-hydrophobic and solvent resistance were fabricated via electrospinning.(1) The PMTFPS-containing block copolymer films with super-hydrophobic andsolvent resistance properties were prepared on an electrospinning equipment undercertain conditions.(2) The results showed that the morphology of electrospun films were variedfrom nanosphere to nanofibers with the increase of the concentration of spinningsolution and polymer molecular weight. And the results of contact angles to water andformamide were correspondingly increased.(3) The diameter of nanofibers presented two aspects of variation: it increasedwith the electric tensile force as a dominant role and it decreased with the flight timeof spinning solution as a dominant role, while it was decreased slightly with theincrease of needle diameter. The morphology of electrospun film changes frombead-free fibers with uniform diameter to fibers with little beads by changing the jetdiameter of the syringe tip from1.0mm to0.3mm.(4) It was found that the microstructure of electrospun films were varied fromnanofibers to nanosphere when the solvent was changed from a mixed solvent ofDMF/THF to DMF, and a great change in contact angle of formamide was happenedat the same time. XPS (X-ray photoelectron spectroscopy) analysis revealed that thereduction of fluorine content on the surface of electrospun films when the solvent was changed from a mixed solvent of DMF/THF to DMF. That is, the contact angle offormamide was more dependent on the morphology of electrospun films, and thenanofibers could give benefit to obtain superhydrophobic and solvent resistanceproperties than nanosphere.