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    Designing effective underwater self-cleaning surfaces by investigating the oil dewetting ability of hydrophobic and underwater superoleophobic Poly(Diisobutyl Glycolide)-Silica composite surfaces
    (Elsevier B.V., 2024) Belen, Sema Nur; Arıcan, Mehmet Onur; Mert, Olcay; Cengiz, Uğur
    This study introduces composite thin films of amphiphilic structures to fabricate underwater superoleophobic surfaces. The hydrophobic part of the structure is created by poly(diisobutyl glycolide) thanks to a side chain of isobutyl groups, while the hydrophilic component is formed with hydrophilic silica nanoparticles. Poly(diisobutyl glycolide), having a 77° water contact angle, was obtained through ring-opening polymerization of L-diisobutyl glycolide in a bulk medium, resulting in excellent conversion (97.9 %) and narrow polydispersity (1.47), while maintaining the chiral center. The investigation revealed a notable increment in the underwater hexadecane contact angle from 110° to 160° In contrast, the water contact angle exhibited partial constancy in the air environment because of the augmenting silica content. At a silica content reached up to 30 %, the self-cleaning underwater oil-repellent surface was accomplished, attributable to the phenomenon of the underwater Cassie state, which effectively trapped air within the hierarchical rough structure. Moreover, the surface free energy (SFE) of the composite films was evaluated using both the van Oss-Chaudary-Good and Owens-Wendt methods. Notably, the contact angle of underwater hexadecane decreased with the increase of polar interactions as determined by both methods, owing to the influence of the underwater Cassie state of the hierarchical composite surface.
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    Öğe
    Symmetric star poly(substituted glycolide) homopolymers and their surface properties
    (Royal Soc Chemistry, 2025) Colak, Yonca; Belen, Sema Nur; Cetin, Duygu; Cengiz, Ugur; Mert, Olcay
    Well-defined star poly(substituted glycolide) (s-PSG) homopolymers with predetermined lengths and numbers of arms, which are alternatives to polylactides and polyglycolides, may offer great opportunity for the modulation of their physical properties, such as glass transition temperature (Tg), crystallinity, hydrophobicity, and surface characteristics due to their geometric and structural differences. Herein, we report the synthesis of s-PSG homopolymers, including a four-armed symmetrical poly(l-diisopropyl glycolide) (4s-PLDIPG) and poly(l-diisobutyl glycolide) (4s-PLDIBG) from the ring opening polymerization (ROP) of their monomers in the presence of tin(ii) 2-ethylhexanoate [Sn(Oct)2] as a catalyst and pentaerythritol as an initiator via a core-first approach under melt conditions. 4s-PLDIPG 8 exhibits lower Tg, melting temperature (Tm) and crystallinity % than 4s-PLDIPG 10 (Tg: 33.7 degrees C vs. 35.9 degrees C; Tm: 143.9 degrees C vs. 183.4 degrees C; Xc: 16.7% vs. 19.1%) due to its lower Mn per arm. 4s-PLDIPG 8 also has a dramatically lower Tm and crystallinity % than its linear counterpart PLDIPG 17 (Tm: 143.9 degrees C vs. 190.6 degrees C; Xc: 16.7% vs. 26.7%) due to its short arm length. As the side chain length of s-PSG homopolymers increased, there was a corresponding increase in the water contact angles and surface roughness values of the thin films, while the surface free energy decreased. This correlation between side chain length and surface properties was further validated by SEM and AFM profiles, which confirmed the impact of extended side chains on the polymer's surface characteristics.