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Applicability of Cassie-Baxter equation for superhydrophobic fluoropolymer silica composite films
(Elsevier, 2015) Cengiz, Ugur; Cansoy, C. Elif
In this study, surface topographies and wettabilities of flat and composite rough films of perfluoro-styrene (TM/S) random copolymers with silica particles were investigated. The water and oil repellencies of flat TM/S copolymer and rough silica-TM/S composite surfaces were studied with varying perfluoro and silica contents. Increase in silica content resulted in an increase in water contact angle values; water contact angle values increased from 113 up to 170, and the resultant surfaces were showing extremely superhydrophobic behavior depending on their silica contents. However a decrease in hexadecane contact angles from 61 to 25 depending on both silica %wt and perfluoro content of the TM/S copolymer was seen. Applicability of Cassie-Baxter equation was also investigated for TM/S copolymer films with silica particles. The results showed that Cassie-Baxter equation cannot be used for superhydrophobic surfaces, however, can be applied to oleophilic surfaces with caution. The oil repellencies of TM/S flat films in the terms of contact angle hysteresis was also compared with perfluoroethyl alkyl methacrylate-methyl methacrylate copolymer (TM/MMA) by using oil drops with varying surface tensions between 20.9 mN/m and 26.9 mN/m. The surface oleophobicities were changed according to the characteristics of the functional groups of MMA and S. The dependency of work of adhesion results of TM/S flat surfaces on wt.% of perfluoroalkyl content was also examined. (C) 2015 Elsevier B.V. All rights reserved.
Bioplastic Production from Microalgae: A Review
(Mdpi, 2020) Cinar, Senem Onen; Chong, Zhi Kai; Kucuker, Mehmet Ali; Wieczorek, Nils; Cengiz, Ugur; Kuchta, Kerstin
Plastic waste production around the world is increasing, which leads to global plastic waste pollution. The need for an innovative solution to reduce this pollution is inevitable. Increased recycling of plastic waste alone is not a comprehensive solution. Furthermore, decreasing fossil-based plastic usage is an important aspect of sustainability. As an alternative to fossil-based plastics in the market, bio-based plastics are gaining in popularity. According to the studies conducted, products with similar performance characteristics can be obtained using biological feedstocks instead of fossil-based sources. In particular, bioplastic production from microalgae is a new opportunity to be explored and further improved. The aim of this study is to determine the current state of bioplastic production technologies from microalgae species and reveal possible optimization opportunities in the process and application areas. Therefore, the species used as resources for bioplastic production, the microalgae cultivation methods and bioplastic material production methods from microalgae were summarized.
Development of a superhydrophobic and superoleophilic halloysite nanotube/phenyltriethoxysilane-coated melamine sponge sorbent material with high performance in supercritical CO2 atmosphere for the selective and effective oil spill cleanup and oil-water separation
(Academic Press Ltd- Elsevier Science Ltd, 2025) Duman, Osman; Cengiz, Candan; Diker, Ceren Ozcan; Cengiz, Ugur; Guresir, Suleyman Mert; Tunc, Sibel
In this study, activated halloysite nanotube (HNT) and phenyltriethoxysilane (PTES) were utilized for the first time to fabricate modified HNT materials and coat them onto melamine sponge (MS) substrate in the supercritical carbon dioxide (scCO2) atmosphere. The successful coating of MS substrate was confirmed using SEM, EDS, XPS, and contact angle measurements. The drainage technique applied in the CO2 medium achieved the uniform coating of both the inner and outer surfaces of the MS. Water and oil contact angles of the fabricated sorbent material (MS-PTES) were measured as 167.1 degrees and 0 degrees, respectively. MS-PTES sorbent having superhydrophobic and superoleophilic properties demonstrated sorption capacities ranging from 47.6 g/g to 132.2 g/g for 13 different pollutants, including various petroleum products, oils, and organic solvents. Moreover, the MSPTES sorbent material showed outstanding separation efficiency (99.99%) for the diesel-water mixture using a continuous separation process. It also displayed high selectivity for oil and organic solvent pollutants under acidic, saline, and alkaline conditions, along with excellent reusability, chemical stability, robustness, and mechanical flexibility. MS sorbent material coated with HNT-modified PTES nanoparticles, produced in the scCO2 atmosphere using the drainage technique, represents a promising solution for the removal of petroleum derivatives, oils, and organic solvents from water.
Effect of alkoxysilane chain length on the surface, stability, sorption and oil-water separation properties of novel superhydrophobic porous sorbent materials produced using innovative drainage technique in scCO2 atmosphere
(Elsevier, 2024) Duman, Osman; Cengiz, Candan; Diker, Ceren Ozcan; Cengiz, Ugur; Guresir, Sueleyman Mert; Tunc, Sibel
Alkoxysilanes play an important role in the development of new superhydrophobic sorbent materials with high sorption capacity for the cleanup of oil spills from water. Here, three different alkoxysilanes with 1, 8 and 16 carbon (C) chains were used for the first time to elucidate the role of alkoxysilanes and to determine the relation between the functional alkyl chain length of alkoxysilane compound within the coating formulation and the surface, sorption and separation properties of novel superhydrophobic sorbent materials fabricated in scCO2 atmosphere. Both the modification of activated halloysite nanotube (HNT) with each methyltrietoxysilane (METES), octyltriethoxysilane (OTES) and hexadecyltrimethoxysilane (HDTMS) separately and the direct fabrication of melamine sponge (MS)-HNT/alkoxysilane hybrid composite sorbents (MS-METES, MS-OTES and MS-HDTMS) were achieved by innovative drainage technique in scCO2 atmosphere. The surface properties of superhydrophobic sorbents were examined using contact angle, SEM, EDS, FTIR, XPS and 29Si-MAS NMR techniques. Maximum sorption capacity of melamine sponge-based hybrid materials decreased from 122.2 g/g to 90.4 g/g as the chain length of alkoxysilane was increased from C1 to C16. Water contact angle, density and porosity of superhydrophobic MS-METES, MS-OTES and MS-HDTMS sorbents were determined to be 153.0 degrees, 13.56 mg/cm3 and 99.10 %; 159.4 degrees, 16.58 mg/cm3 and 98.90 %; and 165.4 degrees, 18.90 mg/cm3 and 98.75 %, respectively. All sorbents exhibited excellent thermal stability, good chemical stability, good robustness, and high mechanical durability. Experimental results revealed that the novel coating technique applied to porous MS have a significant potential for the direct fabrication of new superhydrophobic and superoleophilic sponge-based sorbent materials.
Fabrication and application of superhydrophilic antifog surface by sol-gel method
(Elsevier Science Sa, 2019) Kaya, Ayse Senem Topcu; Cengiz, Ugur
Herein, we report a single step and a one pot by using spin coating method for the preparation of optically transparent, superhydrophilic, antifogging composite surface. The wettability performance and also antifogging properties of these surfaces were investigated depending on silica particles content in composite solution. It was also examined the effects of production technique changes on wettability and antifogging characteristics of these surfaces having 20% wt silica particles content. The apparent water contact angle of transparent surfaces were found to vary between 65 degrees and 4 degrees depending on the silica content, polymer type and production technique. Superhydropilic surface (WCA = 4 degrees) displayed a good antifogging performance and light permeability behavior. It was also observed that antifogging behavior kept showing when water contact angle is lower than 15 degrees. However, antifogging properties disappeared when water contact angle is higher than 25 degrees. These results were showed that one step-one pot reaction have a better results than two step reactions depending on silica particles adding time.
Fabrication and characterization of metakaolin-based fiber reinforced fire resistant geopolymer
(Elsevier, 2023) Akarken, Gurkan; Cengiz, Ugur
Geopolymers have many advantages over Portland cement, such as low energy cost, reduced greenhouse gas emissions, high compressive strength, high-temperature stability, low thermal conductivity, and high strength at an early age. This study obtained fiber-reinforced geopolymer composite (FRGC) structures using metakaolin (MK) basalt and glass fiber, and the fire-resistant FRGC structure was developed. The morphology, structure, and thermal characterization of fire-resistant FRGC were obtained using SEM, TEM, XRD, XRF, FTIR, and TGA. As a result of SEM, FT-IR, and TGA analyses, it was observed that high-temperature geopolymer samples retained their stable structure. The SEM images also indicated the fiber's effect on preventing surface cracking. Fireresistant properties were tested by heat exposure in a muffle furnace for thermal behavior of 200, 400, and 800 degrees C. The mechanical stability of the FRGC blocks was tested using the compression test before and after exposure to high temperatures. In this test, the FRGC block, kept for one hour at 200 degrees C, still has the compressive strength at the high strength concrete class and can be used in skyscrapers (51-76 MPa).
Fabrication of superhydrophobic melamine sponge composite sorbent in supercritical carbon dioxide atmosphere for selective and effective oil removal from water
(Elsevier Sci Ltd, 2023) Duman, Osman; Cengiz, Ugur; Diker, Ceren Ozcan; Cengiz, Candan; Guresir, Sueleyman Mert; Tunc, Sibel
In this study, both the modification of activated halloysite nanotube (HNT) with methyltriethoxysilane (METES) and the fabrication of durable, superhydrophobic (water contact angle: 153.0 degrees) and superoleophilic (oil contact angle: 0 degrees) melamine sponge (MS)-HNT-METES sorbent material (MS-METES) were achieved in supercritical carbon dioxide (scCO2) atmosphere. For the coating of MS with clay mineral and METES through sol-gel reaction in scCO2, optimal process conditions were determined to be pressure difference of 60 bars at 35 degrees C, solvent/ METES mass ratio of 7.5, METES/MS mass ratio of 10, and degas time of 400 s. Successful preparation of MSMETES was proven by XPS, FTIR, 29Si-MAS NMR, SEM, and contact angle measurements. MS-METES displayed excellent sorption capacity for various petroleum products, oils, and organic solvents (49.6-122.4 g/g), remarkable oil-water separation efficiency (99.1%, for continuous separation technique), high selectivity for oil/ organic solvent in acidic, salty, and alkaline solution conditions, good reusability, chemical stability and robustness, and outstanding flexibility and mechanical stability. We believe that the innovative process used in this study will have great potential to be used by researchers in the direct fabrication of new superhydrophobic and superoleophilic sorbent materials for the selective removal of oil and organic solvent spills from water.
Fabrication of superhydrophobic sorbent material via in-situ coating of melamine sponge with halloysite nanotube and fluoroalkylsilane using supercritical CO2 coating system for efficient oily water treatment
(Elsevier, 2025) Duman, Osman; Cengiz, Ugur; Diker, Ceren Ozcan; Guresir, Sueleyman Mert; Tunc, Sibel; Cengiz, Candan
This study presents the preparation of a novel sorbent material with high performance and special wettability for oily water treatment, utilizing halloysite nanotube (HNT) and perfluorooctyl triethoxysilane (PFOTES). Fluoroalkyl silanes, such as PFOTES, offer significant advantages over other monomers and alkoxysilanes due to their superior water-repellent properties and high solubility in CO2 atmosphere, enabling homogeneous polymerization and coating. The modification of PFOTES with HNT was successfully achieved in the supercritical CO2 (scCO2) environment at 35 degrees C and 125 bar using a sol-gel technique. Subsequently, HNT-modified PFOTES nanoparticles were coated onto melamine sponge (MS) via a drainage technique, marking the first application of this method to create a superhydrophobic (WCA: 165.2 degrees) and superoleophilic (OCA: 0 degrees) sorbent material (MSPFOTES). The MS-PFOTES sorbent material, produced via a one-step, two-pot coating method, demonstrated exceptional sorption capacities ranging from 39.1 to 117.5 g/g for oily pollutants / organic solvents. Additionally, MS-PFOTES achieved an outstanding separation efficiency of 99.99 % for diesel-water mixtures in continuous separation processes. The fabricated material also exhibited remarkable thermal stability, chemical resistance, and robustness. Experimental findings obtained in this study highlight the significant potential of this innovative coating technique for the direct preparation of sorbent material with special wettability for oily water treatment.
PEG-functionalized carbazole-based polymers for UV-protected hydrophilic glass coatings
(Elsevier Science Sa, 2023) Altinisik, Sinem; Kortun, Arzu; Nazli, Ahmet; Cengiz, Ugur; Koyuncu, Sermet
The UV-absorbing and non-fogging glass coatings containing carbazole-based conjugated backbone with different lengths of hydrophilic PEG subunit (KP-PEG) were produced. The characterizations of the polymers were carried out by using different techniques such as FT-IR, 1H NMR, GPC, TGA and DSC. Transmittance and thin-film morphology analyses, which are essential for UV protection and wettability, were investigated by UV-Vis absorption, AFM and TEM techniques, respectively. Transparent thin films prepared by the polymer solutions in chloroform were obtained by spin coating method at a scan rate of 2000 rpm. The wettability performance and antifogging properties of these surfaces were investigated depending on the PEG length in the polymer subunit. The water contact angle of the surfaces was improved to the range between 60 degrees and 29 degrees depending on the amount of PEG group. KP-PEG750 is the best polymer thin film in terms of having the highest roughness, optimum UV absorption and the low contact angle value.
Perfluoromethacrylate-styrene statistical copolymers synthesized in CO2-expanded monomers
(Springer, 2014) Cengiz, Ugur; Erbil, H. Yildirim
Statistical copolymers of perfluoroalkyl ethyl methacrylate (Zonyl-TM) and styrene (S) were synthesized in CO2-expanded monomer medium at a low initial pressure of 25 MPa. Different Zonyl-TM/S feed ratios were used during copolymerizations, and it was determined that the increase in the Zonyl-TM content and decrease of the CO2 amount in the comonomer feed resulted in a decrease of the molecular weights of copolymers due to earlier precipitation of copolymers giving shorter chains. The cloudy CO2-expanded liquid monomer phase was found to be the main loci of copolymerization. In addition, the increase in the Zonyl-TM feed ratio resulted in an increase in the critical degree of the polymerization time (J (crit)) as the time when the copolymer chains start to precipitate. The higher the Zonyl-TM content used in the feed, the higher the J (crit) time and the lower the weight-average molecular weight (M (w)) of the copolymer obtained. Thermal analysis results of the copolymer indicated that the copolymers are stable up to 387-403 A degrees C.
Preparation of stable, transparent superhydrophobic film via one step one pot sol-gel method
(Springer, 2018) Topcu, Ayse Senem Kaya; Erdogan, Edanur; Cengiz, Ugur
Herein, we report a single step and a one pot by using spin coating method for the preparation of optically transparent superhydrophobic TEOS-silica composite films. Silica sols were prepared by keeping the molar ratio of TEOS/CH3OH/H2O (0.1 M NH4F) constant at 1:33.15:6.06, respectively. Increasing the silica content of the coating solution resulted in decreasing the transparency of the composite films from 93 to 84% (in references to 93% transmission defined by a plain glass substrate). The static water and hexadecane contact angle of transparent surfaces were found to vary between 65A degrees and 170A degrees (sliding angle < 3A degrees) and 45A degrees to 5A degrees (sliding angle = 15A degrees) depending on the silica content. The stability of the surface remained nearly constant for several months under stored at ambient conditions. The mechanical stability of the prepared of TEOS-silica composite was tested by scratching and adhesive tape test. For the chemical test applications, NaOH, HCl, and H2SO4 were used for the TEOS-silica composite films.
Self-cleaning superhydrophobic polyester resin production for gel coat applications
(Elsevier Science Sa, 2025) Akarken, Gurkan; Cengiz, Ugur; Ozturk, Nagihan; Balkaner, Ceyda
This research aimed to develop a superhydrophobic unsaturated polyester resin for gel coat applications, hypothesizing that modifying the primary component, polyester resin, to be superhydrophobic would impart the same property to the gel coat. To achieve this, coating solutions were prepared using two different strategies. The first approach involved complementing resin modification with a condensation reaction. The second strategy involved modifying the polyester resin through simultaneous radicalization and condensation polymerization. The superhydrophobic, self-cleaning gel coat applications were applied using a spray coating technique. Subsequently, wettability tests, including contact angle measurements and self-cleaning performance assessments, as well as surface morphology analyses using SEM, AFM, and XPS, were conducted. Additionally, structural characterizations of the composite material were performed using FTIR, XRD, and TGA. The water contact angle of the unmodified polyester resin, initially 84 degrees, increased to 173 degrees, demonstrating the successful production of superhydrophobic polyester resin. It is believed that the produced gel coat will not only result in significant labor savings due to its self-cleaning properties and corrosion protection but will also reduce the use of environmentally harmful cleaning agents.
Solvent-Free Synthesis of a Superamphiphobic Surface by Green Chemistry
(Amer Chemical Soc, 2019) Ozbay, Salih; Cengiz, Ugur; Erbil, H. Yildirim
A superamphiphobic surface having both water and oil repellence was prepared by applying a solvent-free surface coating method using liquid-CO2 in the scope of green chemistry. Poly(perfluoroalkyl ethyl acrylate) homo- polymer was synthesized by a free radical polymerization in supercritical CO2 medium. This polymer was dissolved in liquid-CO2 containing hydrophilic nanosilica particles in a stirred stainless steel reactor at room temperature under a low CO2 pressure. The polymer/nanosilica dispersion was used to coat glass slides located horizontally in a stainless steel tube by using the free meniscus coating method. A series of superamphiphobic coatings were formed under different coating conditions with the variation of polymer/nanosilica concentrations, the types of nanosilica powders, system pressures, and degassing flow rates. The highest apparent water contact angle was 173 degrees and the hexadecane contact angle was 169 degrees on these superamphiphobic hybrid coatings with roll-off angles that were <7 degrees. Such superamphiphobic surfaces have a large potential in biomedical applications for the preservation of small amounts of bioliquids during analysis. In a parallel study, a superhydrophobic surface without containing any nanosilica powder was also obtained by applying the rapid expansion supercritical solution method. Polyperfluoroacrylate polymer was dissolved in supercritical CO2 and was sprayed onto glass slides that were previously coated with a polyacrylate adhesive layer. The water contact angles were larger than 170 degrees on this superhydrophobic coating. To optimize the coating conditions, the cloud point pressures of polyperfluoroacrylate polymer in sc-CO2 were determined at various polymer concentrations and temperatures for this purpose.
Supercritical CO2-Mediated Decellularization of Bovine Spinal Cord Meninges: A Comparative Study for Decellularization Performance
(Amer Chemical Soc, 2024) Ozudogru, Eren; Kurt, Tugce; Derkus, Burak; Cengiz, Ugur; Arslan, Yavuz Emre
The extracellular matrix (ECM) of spinal meninge tissue closely resembles the wealthy ECM content of the brain and spinal cord. The ECM is typically acquired through the process of decellularizing tissues. Nevertheless, the decellularization process of the brain and spinal cord is challenging due to their high-fat content, in contrast to the spinal meninges. Hence, bovine spinal cord meninges offer a promising source to produce ECM-based scaffolds, thanks to their abundance, accessibility, and ease of decellularization for neural tissue engineering. However, most decellularization techniques involve disruptive chemicals and repetitive rinsing processes, which could lead to drastic modifications in the tissue ultrastructure and a loss of mechanical stability. Over the past decade, supercritical fluid technology has experienced considerable advancements in fabricating biomaterials with its applications spreading out to tissue engineering to tackle the complications mentioned above. Supercritical carbon-dioxide (scCO2)-based decellularization procedures especially offer a significant advantage over classical decellularization techniques, enabling the preservation of extracellular matrix components and structures. In this study, we decellularized the bovine spinal cord meninges by seven different methods. To identify the most effective approach, the decellularized matrices were characterized by dsDNA, collagen, and glycosaminoglycan contents and histological analyses. Moreover, the mechanical properties of the hydrogels produced from the decellularized matrices were evaluated. The novel scCO2-based treatment was completed in a shorter time than the conventional method (3 versus 7 days) while maintaining the structural and mechanical integrity of the tissue. Additionally, all hydrogels derived from scCO2-decellularized matrices demonstrated high cell viability and biocompatibility in a cell culture. The current study suggests a rapid, effective, and detergent-free scCO2-assisting decellularization protocol for clinical tissue engineering applications.
Superhydrophobic melamine sponge-sorbent fabricated using WS2, halloysite nanotube, octyltriethoxysilane, tetraethoxysilane, and polydimethylsiloxane for the selective uptake of oil from water
(Elsevier, 2023) Duman, Osman; Diker, Ceren Ozcan; Guresir, Sueleyman Mert; Cengiz, Ugur; Tunc, Sibel
Here, a novel coating formulation was developed using WS2, halloysite nanotube (HNT), octyltriethoxysilane (OTES), tetraethoxysilane (TEOS), and polydimethylsiloxane (PDMS) to fabricate a new melamine sponge (MS)-based superhydrophobic sorbent material for the treatment of wastewater polluted with oily substances and organic solvents. The innovative aspect of this study lies in the alteration of WS2 particle size within the sorbent material and the chemical modification of HNT with silane compounds through the formation of reactive -OH groups on the cylindrical outer surface of clay mineral by chemical activation. The effect of nano- and micro-WS2 particle sizes on the wettability of sorbent material was investigated systematically. Successful coating of MS with the developed coating formulation was confirmed using SEM, mapping, EDS, and FTIR analyses. Sorbent material showed remarkable superhydrophobicity (WCA: 170.3 degrees), excellent thermal and mechanical stability, good chemical durability, high sorption capacity (34.0-73.8 g/g), good reusability, outstanding oil-water separation ability (>99.8 %) and flux (11,774 L/(m(2).h)), and efficient separation ability for water-in-oil emulsions (up to 99.6 %). The results of this study exhibit that MS/WS2/HNT/OTES-TEOS/PDMS sorbent material is of a great potential for the selective and effective removal of oily substance and organic solvent spills from water.
Superhydrophobic perfluoropolymer surfaces having heterogeneous roughness created by dip-coating from solutions containing a nonsolvent
(Elsevier Science Bv, 2014) Cengiz, Ugur; Erbil, H. Yildirim
Superhydrophobic and oleophobic rough copolymer surfaces containing micro- and nano-hierarchical ball-like islands having diameters between 100 nm and 7 mu m were formed using styrene-perfluoromethacrylate random copolymers which were dip-coated on glass slides from THF and MEK mixture containing methanol as nonsolvent. These copolymers were synthesized in a CO2-expanded monomer medium at 250 bar pressure and 80 degrees C. The sizes of the micro-islands can be controlled by varying the copolymer composition; and the degree of phase separation by adjusting the solvent/non-solvent ratio. Flat and lotus-like hierarchical surfaces of the copolymers were characterized using contact angle measurements and SEM. The increase in the perfluoromethacrylate content of the flat copolymers resulted in a decrease of the total surface free energy of the flat copolymer surfaces from 18.3 down to 14.2 mJ/m(2). The increase in the methanol non-solvent fraction resulted in decrease of the micro-island diameter from 7 mu m down to 100 nm and the water contact angle increased from 117 degrees up to 160 degrees and hexadecane from 65 degrees up to 90 degrees. (C) 2013 Elsevier B.V. All rights reserved.
Superhydrophobic perfluoropolymer/polystyrene blend films induced by nonsolvent
(Elsevier Science Bv, 2016) Gengec, Nevin Atalay; Cengiz, Ugur; Erbil, H. Yildirim
Statistical copolymers of perfluoroalkyl ethyl acrylate (Zonyl-TAN) and methyl methacrylate (MMA) were synthesized in a CO2 polymerization system where a CO2-expanded monomer mixture was formed at 13 MPa, and 80 degrees C by using AIBN as initiator. Flat and superhydrophobic surfaces were subsequently prepared on glass slides by applying a phase separation process where the synthesized p(TAN-co-MMA) copolymer and polystyrene (PS) were dissolved in THE solvent. Ethanol was added as the non-solvent to introduce superhydrophobicity during film formation. Water contact angle on the flat p(TAN-co-MMA) copolymer was 118 degrees and increased up to 170 degrees with the formation of surface roughness. The ratio of the ethanol non-solvent in the blend solution has an important effect on the magnitude of surface roughness during the phase separation process. Both pits and protrusions of 1-10 mu m in size were formed on the surface when non-solvent was used. Surface roughness increased with the increase in the ethanol ratio and the PS content of the blend solution. (C) 2016 Elsevier B.V. All rights reserved.
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.
Synthesis of Silica-Based Boron-Incorporated Collagen/Human Hair Keratin Hybrid Cryogels with the Potential Bone Formation Capability
(Amer Chemical Soc, 2021) Cal, Fatma; Sezgin Arslan, Tugba; Derkus, Burak; Kiran, Fadime; Cengiz, Ugur; Arslan, Yavuz Emre
Tissue engineering and regenerative medicine have evolved into a different concept, the so-called clinical tissue engineering. Within this context, the synthesis of next-generation inorganic-organic hybrid constructs without the use of chemical crosslinkers emerges with a great potential for treating bone defects. Here, we propose a sophisticated approach for synthesizing cost-effective boron (B)- and silicon (Si)-incorporated collagen/hair keratin (B-Si-Col-HK) cryogels with the help of sol-gel reactions. In this approach, collagen and hair keratin were engaged with a B-Si network using tetraethyl orthosilicate as a silica precursor, and the obtained cryogels were characterized in depth with attenuated total reflectance-Fourier transform infrared spectroscopy, solid-state NMR, X-ray diffraction, thermogravimetric analysis, porosity and swelling tests, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda analyses, frequency sweep and temperature-dependent rheology, contact angle analysis, micromechanical tests, and scanning electron microscopy with energy dispersive X-ray analysis. In addition, the cell survival and osteogenic features of the cryogels were evaluated by the MTS test, live/dead assay, immuno/histochemistry, and quantitative real-time polymerase chain reaction analyses. We conclude that the B-Si-networked Col-HK cryogels having good mechanical durability and osteoinductive features would have the potential bone formation capability. © 2021 American Chemical Society.
Synthesis, Hydrolytic Degradation Behavior, and Surface Properties of Poly(alkyl glycolide)-Polyglycolide Copolymers
(Amer Chemical Soc, 2025) Bamyaci, Mehtap Canturk; Cetin, Duygu; Cengiz, Candan; Belen, Sema Nur; Mert, Olcay; Cengiz, Ugur; Mert, Serap
Given the environmental impact of polymers on our daily lives, the development of biodegradable polymers is becoming increasingly critical. Poly(diisobutyl glycolide)-polyglycolide (PDIBG-PGA) and poly(diisopropyl glycolide)-polyglycolide (PDIPG-PGA) copolymers, which are structurally similar to polylactic-co-glycolic acid (PLGA) polyesters frequently used in the field of biomaterials, were synthesized via ring-opening polymerization (ROP) of glycolide with l-diisobutyl glycolide (l-DIBG) or l-diisopropyl glycolide (l-DIPG), respectively, in various molecular weights (M w GPC: 15.5-40.0 kDa) and in high yields (up to 85.0%). The wettability characteristics of biodegradable polymers are important not only in air but also for their behavior in underwater environments. PDIBG-PGA silica composites, due to their amphiphilic nature, exhibited water contact angles between 72 degrees and 85 degrees in air, unaffected by the increasing addition of hydrophilic silica nanoparticles. However, underwater-oil contact angles increased from 75 degrees to 165 degrees as a result of the higher silica nanoparticle content and enhanced surface roughness. When the silica content reached 30%, the surface demonstrated self-cleaning and oil-repellent properties underwater, attributed to the Cassie state, which trapped air within the surface's hierarchical roughness. Furthermore, the surface free energy (SFE) values of PDIBG-PGA and PDIPG-PGA copolymer films were evaluated using the Owens-Wendt method, which revealed an increasing underwater hexadecane contact angle as the polar component interactions increased. Differential scanning calorimetry analysis revealed that all synthesized copolymers were amorphous, and the glass transition temperatures (T g) increased with the increase in the molecular weight of the copolymers (for instance, M n GPC: 9560 g/mol -> T g: 25.1 degrees C vs M n GPC: 20,850 g/mol -> T g: 32.3 degrees C for PDIBG-PGA; M n GPC: 10,670 g/mol -> T g: 37.7 degrees C vs M n GPC: 23,360 g/mol -> T g: 42.3 degrees C for PDIPG-PGA). The molecular weight decreases of 88.3% and 76.5% and mass losses of 36.7% and 12.3% were observed for PDIBG-PGA and PDIPG-PGA copolymers after 8 weeks of hydrolytic degradation, respectively. The faster degradation of PDIBG-PGA (T g: 25.1 degrees C) than PDIPG-PGA (T g: 37.7 degrees C) may be attributed to the T g below the hydrolytic degradation temperature (37 degrees C) because of an increase in the mobility of PDIBG-PGA polymer chains, allowing water molecules to transfer more easily through the matrix.

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