Optimization of the preparation of novel polymer/clay nanocomposites

Recent advances in material technologies have resulted in the preparation of novel polymer/clay composites with improved thermal, mechanical, optoelectronic/ magnetic properties and increased biodegradability [1]. In this study, six samples of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (PGME) nanocomposites with organically-modified montmorillonite clay Cloisite 30B® (C30B), were prepared via suspension copolymerization. In order to obtain nanocomposites with fine spherical beads of regular shape and satisfying thermal stability the optimization of the synthesis conditions was performed. Firstly, the influence of the poly(N-vinyl pyrrolidone) (PVP) quantity in the aqueous phase was varied (1, 3 and 5 wt.%) at a constant stirring rate of 250 rpm and constant clay content C30B (10 wt.%). In the second phase of the optimization of the preparation, samples with a constant composition of the composite reaction mixture (5 wt.% PVP and 10 wt.% C30B) at a stirring rate of 250, 325 and 400 rpm, were prepared. According to the obtained results, it was concluded that the optimal conditions for preparation of these composites are 5 wt.% of PVP and 400 rpm. The prepared nanocomposites were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) in air. The structure of the prepared nanocomposites was confirmed with FTIR spectroscopy. According to the obtained SEM microphotographs the fine spherical beads, with desired size and homogeneous morphology, were prepared. Furthermore, SEM analysis was also showed that clay nanoparticles are homogeneously dispersed both inside surface and cross-section area. The incorporation of C30B clay increased the thermal stability of the prepared polymer/clay nanocomposites in comparison to the pure PGME copolymer

Optimization of the preparation of novel polymer/clay nanocomposites

Recent advances in material technologies have resulted in the preparation of novel polymer/clay composites with improved thermal, mechanical, optoelectronic/ magnetic properties and increased biodegradability [1]. In this study, six samples of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (PGME) nanocomposites with organically-modified montmorillonite clay Cloisite 30B® (C30B), were prepared via suspension copolymerization. In order to obtain nanocomposites with fine spherical beads of regular shape and satisfying thermal stability the optimization of the synthesis conditions was performed. Firstly, the influence of the poly(N-vinyl pyrrolidone) (PVP) quantity in the aqueous phase was varied (1, 3 and 5 wt.%) at a constant stirring rate of 250 rpm and constant clay content C30B (10 wt.%). In the second phase of the optimization of the preparation, samples with a constant composition of the composite reaction mixture (5 wt.% PVP and 10 wt.% C30B) at a stirring rate of 250, 325 and 400 rpm, were prepared. According to the obtained results, it was concluded that the optimal conditions for preparation of these composites are 5 wt.% of PVP and 400 rpm. The prepared nanocomposites were characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) in air. The structure of the prepared nanocomposites was confirmed with FTIR spectroscopy. According to the obtained SEM microphotographs the fine spherical beads, with desired size and homogeneous morphology, were prepared. Furthermore, SEM analysis was also showed that clay nanoparticles are homogeneously dispersed both inside surface and cross-section area. The incorporation of C30B clay increased the thermal stability of the prepared polymer/clay nanocomposites in comparison to the pure PGME copolymer

Structural, thermal and surface characterization of thermoplastic polyurethanes based on poly(dimethylsiloxane)

In this study, the synthesis, structure and physical properties of two series of thermoplastic polyurethanes based on hydroxypropyl-terminated poly(dimethylsiloxane) (HP-PDMS) or hydroxyethoxypropyl-terminated poly(dimethylsiloxane) (EO-PDMS) as soft segments, and 4,4'-methylenediphenyl diisocyanate and 1,4-butanediol as hard segments were investigated. The polyurethanes were synthesized by two-step polyaddition in solution. The effects of the type and content of PDMS segments on the structure, thermal and surface properties of copolymers were studied by H-1-, C-13-nuclear magnetic resonance (NMR) spectroscopy and two-dimensional NMR spectroscopies (heteronuclear multiple bond correlation (HMBC) and rotating-frame nuclear Overhauser effect (ROESY)), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide-angle X-ray scattering (WAXS), scanning electron microscopy (SEM) and water contact angle and water absorption measurements. Thermal properties investigated by DSC indicated that the presence of soft PDMS segments lowers the glass transition and melting temperatures of the hard phase as well as the degree of crystallinity. SEM analysis of the copolymers with a lower soft segment content confirmed the presence of spherulite superstructures, which arise from the crystallization of the hard segments. When compared with polyurethanes prepared from HP-PDMS, the copolymers synthesized from EO-PDMS with the same content of the soft segments had a higher degree of crystallinity, better thermal stability and a less hydrophobic surface. The obtained results showed that the synthesized polyurethanes had good thermal and surface properties, which could be further modified by changing the type or content of the soft segments

Supplementary material for the article: Stefanović, I. S.; Špírková, M.; Poreba, R.; Steinhart, M.; Ostojić, S.; Tešević, V.; Pergal, M. V. Study of the Properties of Urethane-Siloxane Copolymers Based on Poly(Propylene Oxide)-b-Poly(Dimethylsiloxane)-b-Poly(Propylene Oxide) Soft Segments. Industrial and Engineering Chemistry Research 2016, 55 (14), 3960–3973. https://doi.org/10.1021/acs.iecr.5b04975

Supplementary material for: [https://doi.org/10.1021/acs.iecr.5b04975]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1918

The association of genetic variants IL2RA rs2104286, IFI30 rs11554159 and IKZF3 rs12946510 with multiple sclerosis onset and severity in patients from Serbia

An algorithm Probabilistic Identification of Causal SNPs, identified 434 causal variants for multiple sclerosis (MS) including IL2RA rs2104286, IFI30 rs11554159 and IKZF3 rs12946510. Analysis of individual and combined effects of these variants in the Serbian population identified that Il2RA rs2104286 G allele carriers had a lower risk for developing MS (gender adjusted OR = 0.63, p = .003). With regard to the IFI30 rs11554159 recessive genetic model, among HLA-DRB1*15:01 positive patients, the AA homozygote had a significantly higher MSSS compared to the G allele carriers (p = .003). This study confirms role of IL2RA rs2104286 in MS and suggest the role of IFI30 rs11554159 in disease severity, which needs validation

Impact of the poly(propylene oxide)-b-poly(dimethylsiloxane)-b-poly(propylene oxide) macrodiols on the surface related properties of polyurethane copolymers

Segmented thermoplastic polyurethane copolymers (PURs) were synthesized using 4,4'-methylenediphenyl diisocyanate and 1,4-butanediol as the hard segment and α,ω-dihydroxy-poly(propylene oxide)-b-poly(dimethylsiloxane)-b-poly(propylene oxide) (PPO-PDMS) as the soft segment. The content of incorporated soft segments in PURs varied in the range from 40 to 90 wt.%. The structure, molecular weights and crystallinity of obtained copolymers were monitored by FTIR, 1H, 2D NMR spectroscopy, GPC and DSC analysis, respectively. Surface free energy analysis indicates the presence of hydrophobic (siloxane) groups on the surface, giving highly hydrophobic nature to the obtained PURs films. Water absorption measurements showed that the increase of the hydrophobic PPO-PDMS segment content, led to the decrease of percentage of absorbed water in copolymers. SEM and AFM analysis revealed that copolymers with lower content of PPO-PDMS segments have higher microphase separation between segments. The results obtained in this work indicate that synthesized PURs based on PPO-PDMS, demonstrated proper surface and morphological properties with a great potential for variety of applications such as hydrophobic coatings in biomedicine. [Projekat Ministarstva nauke Republike Srbije, br. 172062

Bilateral retinal detachment in a case of preeclampsia

Serous retinal detachment is an unusual cause of visual loss in preeclampsia. We report the case of 24-years-old primipara with severe preeclampsia who developed bilateral serous retinal detachment a few hours after delivery. A few weeks after delivery there was spontaneous resorption of the subretinal fluid and complete resolution bilateral serous retinal detachment, with residual pigmentary changes of the retinal pigment epithelium. Visual acuity was normal in each eye. The management of retinal detachment as a complication in preeclampsia is conservative and the prognosis is usually good

Preparation and Characterization of Novel Glycidyl Methacrylate/Clay Nanocomposites

The impact of the type and amounts of nanofiller on the features of the glycidyl methacrylate-co-ethylene glycol dimethacrylate (GMA-co-EGDMA)/organomodified montmorillonite (OMt) nanocomposites that were prepared by in situ radical suspension polymerization, was examined. Cloisite 30B and Cloisite 25A were used in this study as nanofillers, in amounts of 2 and 10 wt.%. The structure, morphology, thermal stability and porosity of the initial GMA-co-EGDMA copolymer and their nanocomposites were examined by ATR-FTIR analysis, wide angle X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and mercury porosimetry. It has been established that both clay nanofillers were successfully incorporated into the structure of the initial copolymer, simultaneously on their surface and also on cross-sectional area. Prepared samples with 2 wt.% have predominantly exfoliated, while samples with 10 wt.% have some tactoids-aggregates structure of the OMt layers. Thermogravimetric analysis revealed that after ~ 30 % of degradation, all nanocomposites become more thermal stable than the initial copolymer. The obtained results indicate that porosity parameters can be easily modified with the addition of clay nanofillers and thus prepared nanocomposites adjusted to specific purposes. © 2022 Authors. Published by association for ETRAN Society

Study of the Properties of Urethane-Siloxane Copolymers Based on Poly(propylene oxide)-b-poly(dimethylsiloxane)-b-poly(propylene oxide) Soft Segments

Segmented polyurethanes (PURs) were prepared from alpha,omega-dihydroxypoly(propylene oxide)-b-poly-(dimethylsiloxane)-b-poly(propyleneoxide) (PPO-PDMS) as the soft segment and 4,4'-diphenylmethane diisocyanate and 1,4-butanediol as the hard segment, via two-step polyaddition process in solvent mixture. The content of hard segments is in the range from 10 to 60 wt %. The structure and composition of PURs are determined by H-1 NMR, C-13 NMR, and ATR-FTIR spectroscopy. Incorporation of PPO-PDMS leads to improvements in thermal stability. Small- and wide-angle X-ray scattering experiments indicate that synthesized PURs with higher content of hard segments have more developed and distinct phase separated morphologies. Dynamic mechanical thermal analysis shows that copolymers have multiple transitions, characteristic for phase-separated systems. The water contact angle increases while water absorption decreases with increasing content of PPO-PDMS segments. The PURs prepared in this work show good thermal, mechanical features with phase separated morphology and high water resistance that enable their widespread application.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3618

Structural, thermal and surface characterization of thermoplastic polyurethanes based on poly(dimethylsiloxane)

In this study, the synthesis, structure and physical properties of two series of thermoplastic polyurethanes based on hydroxypropyl terminated poly(dimethylsiloxane) (HP-PDMS) or hydroxyethoxy propyl terminated poly(dimethylsiloxane) (EO-PDMS) as a soft segment, and 4,4’-methylenediphenyl diisocyanate and 1,4-butanediol as a hard segment were investigated. Each series is composed of samples prepared with a different soft segment. The polyurethanes were synthesized by two-step polyaddition in solution. The effects of the type and content of PDMS segments on the structure, thermal and surface properties of copolymers were studied by 1H NMR, 13C NMR and two-dimensional NMR (HMBC and ROESY) spectroscopy, GPC, DSC, TGA, WAXS, SEM, water contact angle and water absorption measurements. Thermal properties investigated by DSC indicated that the presence of soft PDMS segments lowers the glass transition and melting temperatures of the hard phase as well as the degree of crystallinity. SEM analysis of copolymers with a lower soft segment content confirmed the presence of spherulite superstructures, which arise from the crystallization of the hard segments. When compared with polyurethanes prepared from HP-PDMS, copolymers synthesized from EO-PDMS with the same content of the soft segments have higher degree of crystallinity, better thermal stability and less hydrophobic surface. Our results show that the synthesized polyurethanes have good thermal and surface properties, which could be further modified by changing the type or content of the soft segments