Control of surface wettability in polymethylmethacrylate films

Polymethylmethacrylate (PMMA) is of critical importance due to its properties such as optical transparency, adequate mechanical strength, ease of processing, and film-forming ability. Control of the surface wettability of PMMA is noteworthy for the development of surface-oriented applications. In this study, effects of intrinsic viscosity and composition of solvent/non-solvent mixture on surface wettability of PMMA were investigated. Effect of silica addition on wettability was further investigated in cases where the solvent/non-solvent approach was limited. For this purpose, PMMAs having different intrinsic viscosities were synthesized by free radical polymerization using benzoyl peroxide (BPO) as an initiator. By decreasing the BPO content from 2.77 wt% to 0.35 wt% relative to the monomer feed, intrinsic viscosity values of the synthesized PMMAs gradually increased from 9.13 mL/g to 24.83 mL/g. The obtained PMMAs were coated as films onto glass slides by dip-coating from coating solutions prepared in toluene with varying amounts of methanol added, and wettability of the films was evaluated by contact angle measurements. Water contact angle values of the films varied from 77° to 46°, while surface free energies ranged from 57.41 mJ/m2 to 45.68 mJ/m2 according to geometric mean approach and from 47.05 mJ/m2 to 39.53 mJ/m2 according to acid-base approach, depending on intrinsic viscosity and amount of methanol added to the PMMA/toluene solution. While PMMA films prepared using toluene/methanol mixtures exhibited hydrophilic behavior, it was observed that the water contact angle could be increased up to 128°, with hydrophobic behavior in silica-added films prepared by drop-casting method in toluene. Science Code : 91218 Key Words : Polymethylmethacrylate, contact angle, surface free energy, wettability Page Number : 54 Supervisor : Assoc. Prof. Dr. Salih ÖZBAY Co-supervisor : Dr. Yılmaz MERT