Preparation And Characterization Of Polymer/POSS Superhydrophobicity Hvbrid Fibers

Superhydrophobic materials have excellent water-repelling and self-cleaning properties. Recently, creating micro-nano structure through electrospinning technique has become one of the most important methods to increase surface roughness and obtain superhydrophobic surface. Especially, it is significant to study on the effect of phase separation of multi-phase composite on the structures and properties of their electrospun mats.In this thesis, polymethyl methacrylate (PMMA) and methacrylisobutyl polyhedral oligomeric silsesquioxane (POSS) were used as the studied system. PMMA/POSS blends, PMMA-co-POSS/POSS blends and PMMA-co-POSS copolymers with different phase morphology were prepared by physical blending and chemical copolymerization. The fibers were fabricated via solution electrospinning, and then investigated their morphology structure and properties. Some results are achieved as follows:1) Using2,2-azobisisobutyronitrile (AIBN) as initiator, PMMA-co-POSS copolymers were synthesized in toluene/THF mixed solvent via radical polymerization before precipitated in iced methanol. Results showed that the synthesized product still contained the unreacted POSS, as the PMMA-co-POSS/POSS blends. In order to obtain the pure PMMA-co-POSS copolymer, two different post-processing methods, one is precipitated in n-hexane after dissolved in THF (denoted as two-step precipitation), the other is extracted in n-hexane directly (denoted as one-step extraction), were used to remove the unreacted POSS. Results showed that these two methods can both remove the unreacted POSS, while the latter was better to obtain pure PMMA-co-POSS copolymers.2) TEM results showed that POSS particles could be better dispersed in PMMA-co-POSS copolymer than in PMMA, that is, the compatibility between PMMA-co-POSS and POSS was better than that between PMMA and POSS. The fibers membranes of PMMA/POSS and PMMA-co-POSS/POSS blends were prepared via solution electrospinning. Water Contact Angle (WCA) results showed that the highest WCA for fiber membrane of the PMMA/POSS blend was148.9°, which did not meet the requirement of superhydrophobicity. As to the fiber membrane of the PMMA-co-POSS/POSS blend, its WCA could reach158°. Therefore, it could be concluded that improving compatibility between polymer and nanoparticle was a way to enhance its WCA. However, the Sliding Angle (SA) of fiber membrane of the PMMA-co-POSS/POSS blend was28°, which was not up to the standard of superhydrophobicity yet. To further reduce phase separation, the fiber membrane of PMMA-co-POSS copolymer was obtained. The results showed its WCA was higher than150°and SA decreased to5°, which indicated that the decrease of phase separation may achieve better superhydrophobic property.3) The effects of molecular weight and concentration on the hybrid fiber membranes of PMMA-co-POSS copolymers fabricated via solution electrospinning were investigated. When the solution concentration fixed, with the increase of molecular weight of PMMA-co-POSS copolymer, the structure of fibers changed from pure beads to pure strings, and the WCA increased firstly and then decreased (the highest WCA was higher than175°), while the SA kept increasing. When molecular weights of PMMA-co-POSS fixed, with the increase of the solution concentrations, the structure of fibers also changed from pure beads to pure strings, and the WCA decreased (all of them were higher than150°) while the SA kept increasing. In conclusion, the fiber membranes of PMMA-co-POSS copolymers with beads-on-strings structure had the best superhydrophobic property.