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Mechanical, Thermal and Morphology Properties of Thermoplastic Polyurethane Copolymers Incorporating α,ω-Dihydroxy-[poly(propyleneoxide)-poly (dimethylsiloxane)-poly(propyleneoxide)] of Varying Poly(propyleneoxide) Molecular Weight  [PDF]
Zeliang Dai, Kai Yang, Qingzhi Dong
Open Journal of Synthesis Theory and Applications (OJSTA) , 2015, DOI: 10.4236/ojsta.2015.43005
Abstract: Novel segmented thermoplastic polyurethane (TPU) copolymers were synthesized using two-step solventless bulk polymerization. 4,4’-methylenediphenyl diisocyanate (MDI) and 1,4-Butanediol (BDO) were used to form hard segment of TPU and α,ω-dihydroxy-[poly(propyleneoxide)-poly (dimethylsiloxane)-poly(propyleneoxide)] (α,ω-dihydroxy-(PPO-PDMS-PPO)) was used to form soft segment of TPU, where the molar ratio of the –N=C=O/OH was 1.02 and the hard segment weight percentage was 30%. A series of TPUs were characterized by fourier transform infrared spectroscopy (FT-IR). The investigation of triblock oligomer’s PPO molecular weight impact on the derived TPU’s mechanical properties, thermal performance, surface water repellency and morphology performance was carried by Instron material tester, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), water contact angles (WCA), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDX) and wide angle X-ray diffraction (WAXD), respectively. FT-IR confirmed α,ω-dihydroxy-(PPO-PDMS-PPO) well cooperating into urethane structure and analyzed hydrogen bonding between N-H group with hard segment C=O group and N-H group with soft segment C-O-C group. DSC and WAXD results showed α,ω-dihydroxy-(PPO-PDMS-PPO) segments crystallization. SEM-EDX results showed that the presence of a spherulitic morphology, which arose from the crystallization of the PPO segments. The thermal properties measured by TGA and DSC were slightly affected by molecular weight of PPO and microphase separation. The weight loss of TPUs started between 294°C and 300°C, and Tg was in the range of -70°C to -107°C. TPU copolymers’ surface hydrophobicity property was excellent with WCA range of 95°?to 112°. TPU-3 with 1000 molecular weight PPO has the optimized mechanical properties with tensile strength 16.4 MPa and the modulus at 100% elongation 6.2 MPa and elongation 398%.
Influence of the content of hard segments on the properties of novel urethane-siloxane copolymers based on a poly(ε-caprolactone)-b-poly(dimethylsiloxane)-b-poly(ε- caprolactone) triblock copolymer  [PDF]
Pergal Marija V.,Anti? Vesna V.,Ostoji? Sanja,Marinovi?-Cincovi? Milena
Journal of the Serbian Chemical Society , 2011, DOI: 10.2298/jsc110307146p
Abstract: A series of novel thermoplastic urethane-siloxane copolymers (TPUSs) based on a α,ω-dihydroxy-[poly(ε-caprolactone)-bpoly( dimethylsiloxane)-b-poly(ε-caprolactone)] (α,ω-dihydroxy-PCLPDMS- PCL) triblock copolymer, 4,4?-methylenediphenyl diisocyanate (MDI) and 1,4-butanediol (BD) was synthesized. The effects of the content (9-63 wt. %) of hard urethane segments and their degree of polymerization on the properties of the segmented TPUSs were investigated. The structure, composition and hard segment degree of polymerization of the hard segments were examined using 1H- and quantitative 13C-NMR spectroscopy. The degree of crystallinity of the synthesized copolymers was determined using wide-angle X-ray scattering (WAXS). The surface properties were evaluated by measuring the water contact angle and water absorption. In the series of the TPUSs, the average degree of polymerization of the hard segments was varied from 1.2 to 14.4 MDI-BD units. It was found that average values from 3.8 to 14.4 MDI-BD units were effective segment lengths for crystallization of hard segments, which resulted in an increase in the degree of microphase separation of the copolymers. Spherulite-like superstructures were observed in copolymer films by scanning electron microscopy (SEM), which are believed to arise from the crystallization of the hard segments and/or PCL segments, depending on the content of the hard segments. The surface of the copolymers became more hydrophobic with increasing weight fraction of PDMS. The synthesized copolymers based on a PCL-PDMS-PCL segment showed good thermal stability, which increased with increasing content of soft PDMS segments, as was confirmed by the value of the starting temperature of thermal degradation.
Synthesis of ester-siloxane multiblock copolymers
Anti? Vesna V.,Vu?kovi? Marija V.,Govedarica Milutin N.
Hemijska Industrija , 2004, DOI: 10.2298/hemind0411499a
Abstract: It was shown that the two-stage transesterification/polycondensation reaction in the melt, can successfully be applied for the preparation of poly(butylene terephtalate-dimethylsiloxane) multiblock copolymers. Three series of co-polymers were synthesized, using poly(dimethylsiloxanes) bearing ester (two series) and hydroxy -end groups as reactants. The structure and composition of the obtained copolymers were determined by 1H NMR spectroscopy A mechanism, i.e. an order of reaction steps, involved in the preparation of the copolymers, was suggested.
Blood Compatibility of Amphiphilic Poly(N-α-acrylamide-L-lysine-b-dimethylsiloxane) Block Copolymers  [PDF]
Kazuo Sugiyama, Nobuyuki Tanigawa, Kohei Shiraishi
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2011, DOI: 10.4236/jbnb.2011.24042
Abstract: Amphiphilic block copolymers poly(LysAA-b-DMS) consisting of a hydrophilic poly(N-α-acrylamide-L-lysine) [poly(LysAA)] segment with different molecular weights and a hydrophobic polydimethylsiloxane (PDMS) segment were prepared as follows. The precursor copolymer poly(Boc-LysAA-OtBu-b-PDMS) was obtained from radical polymerization of N-α-acrylamide-N-ε-tert-butoxycarbonyl-L-lysine-tert-butylester (Boc-LysAA-OtBu) initiated with 4,4’-azobis(polydimethylsiloxane 4-cyanopentanoate) (azo-PDMS) with the molecular weight of PDMS Mw = 4.3 × 103 in the presence of 2-mercaptoethanol (2-ME) as a chain-transfer agent. Removal of the protecting groups of the precursor copolymer was carried out in 80% trifluoroacetic acid aqueous solution to give poly(LysAA-b-DMS)-1-3. The weight average molecular weight of poly(LysAA-b-DMS)-1-3 was Mw = 1.02 × 104 – 2.52 × 104. From the 1H-NMR and fluorescence spectra measurements, poly(LysAA-b-DMS)-1-3 was determined to self-organize and form core-shell micelles in water. The critical micelle concentration (CMC) increased to 1000 - 4000 mg·L–1 with increasing molar ratio of the poly(LysAA) segment from 0.42 to 0.65. From morphological analysis with a scanning probe microscope (SPM), poly(LysAA-b-DMS) has microphase-separated structures made up of hydrophilic and hydrophobic regions with the domain size ranging from several tens to several hundreds of nanometers. Inhibition of thrombin activity of poly(LysAA-b-DMS) was evaluated from the Michaelis constant (KM) and catalytic activity (kcat) for the enzymatic reaction of thrombin and synthetic substrate S-2238 in the presence of poly(LysAA-b-DMS). The KM and kcat were 0.10 - 0.11 mM and 4.04 × 105 – 4.26 × 105 min–1, respectively. Fibrinolytic activity was also verified from the transformation of plasminogen to plasmin by tissue plasminogen activator (t-PA) using synthetic substrate S-2251 in the presence of poly(LysAA-b-DMS). The KM and kcat were 0.07 mM and 5.73 × 106 –5.95 × 106 min–1, respectively.
Molecular Dynamics in grafted layers of poly(dimethylsiloxane) (PDMS)  [PDF]
L. Hartmann,P. Pouret,L. Leger,F. Kremer
Physics , 2002, DOI: 10.1063/1.1556852
Abstract: Dielectric relaxation spectroscopy 10^-1 Hz to 10^6 Hz) is employed to study the molecular dynamics of poly(dimethylsiloxane) (PDMS, Mw=1.7 10^5 g/mol and Mw=9.6 10^4 g/mol as grafted films with thicknesses d below and above the radius of gyration Rg. For d smaller than Rg the molecular dynamics becomes faster by up to three orders of magnitude with respect to the bulk resulting in a pronounced decrease of the Vogel temperature T0 and hence the calorimetric glass transition temperature Tg. For d larger than Rg the molecular dynamics is comparable to that of the bulk melt. The results are interpreted in terms of a chain confinement effect and compared with the findings for low molecular eight glass forming liquids contained in nanoporous glasses and zeolites. Crystallization effects - well known for PDMS - are observed for films of thicknesses above and below Rg.
Powdered Milk Consumers’ Buying Behavior  [cached]
Luu Trong Tuan,Nguyen Thi Truc Phuong,Luu Thi Bich Ngoc,Luu Hoang Mai
International Journal of Business and Management , 2012, DOI: 10.5539/ijbm.v8n2p29
Abstract: Following the storm of melamine in milk and lower protein milk index than the published standard, consumers are more and more cautious when they choose powdered milk for their children. More especially, the Vietnamese prefer to buy imported powdered milk rather than domestic powdered milk. Accordingly, this research is conducted to investigate which factors influence consumer-buying behavior toward imported milk powdered in Ho Chi Minh City through a quantitative survey of 110 consumers. Through multiple regression analysis, the findings indicate that product brand, advertisement, and country of origin are significant predictors of consumer-buying behaviors towards imported powdered milk. Sponsorship turned out to be insignificant factor in predicting the dependent variable. Among demographic characteristics only income was found to affect the consumer-buying behavior.
Scatterer induced mode splitting in poly(dimethylsiloxane) coated microresonators  [PDF]
Lina He,Sahin Kaya Ozdemir,Jiangang Zhu,Lan Yang
Physics , 2010, DOI: 10.1063/1.3435480
Abstract: We investigate scatterer induced mode splitting in a composite microtoroidal resonator (Q ~ 10^6) fabricated by coating a silica microtoroid (Q ~ 10^7) with a thin poly(dimethylsiloxane) layer. We show that the two split modes in both coated and uncoated silica microtoroids respond in the same way to the changes in the environmental temperature. This provides a self-referencing scheme which is robust to temperature perturbations. Together with the versatile functionalities of polymer materials, mode splitting in polymer and polymer coated microresonators offers an attractive sensing platform that is robust to thermal noise.
Adsorption of lignosulfonate compounds using powdered eggshell  [PDF]
Muhammad Ali Zulfikar,Edeh Dieke Mariske,Samitha Dewi Djajanti
Songklanakarin Journal of Science and Technology , 2012,
Abstract: Batch adsorption of lignosulfonates using untreated powdered eggshell under the influences of mixing time, pH,particle size and dose of powdered eggshell was investigated. Adsorption isotherms of lignosulfonates onto powder eggshellwere also studied. Eggshells were collected from the Balubur traditional market in Bandung, Indonesia, washed with distilledwater, air dried, and then ground into powder of different particle sizes. Kinetic studies found that equilibrium time was ashigh as 90 minutes. From experiments carried out at different pH, it was observed that pH plays an important role in theadsorption of lignosulfonate compounds. It was also observed that particles size has no significant effect on the adsorptionof lignosulfonate compounds. The optimum dosage of powdered eggshell was 30 g/100 mL of 500 mg/L lignosulfonatesolution. Adsorption isotherms studied through the use of graphical methods revealed that the adsorption of lignosulfonatesonto powdered eggshell follows the Langmuir model.
Major and Trace Element Levels in Powdered Milk  [PDF]
E.O. Akpanyung
Pakistan Journal of Nutrition , 2006,
Abstract: Six commercial brands of powdered milk produced in Nigeria were analyzed for their major and trace element composition. The products were found to be good sources of mineral nutrients except for sodium. This paper suggests the need for regular intake of this brand of processed milk so as to derive optimal benefits from its reservoir of major and trace elements.
Synthesis of gold-poly (dimethylsiloxane) nanocomposite through a polymer-mediated silver/gold galvanic replacement reaction
Pooja Devi,Simona Badilescu,Muthukumaran Packirisamy,Pethaiyan Jeevanandam
Gold Bulletin , 2010, DOI: 10.1007/BF03215000
Abstract: Silver-poly (dimethylsiloxane) nanocomposite films are prepared by an in-situ synthesis by incubating the polymer film in a silver nitrate aqueous solution and using the reducing properties of the polymer’s curing agent. Silver nanoparticles concentrated in the surface layer of the silver-poly (dimethylsiloxane) nanocomposite are further replaced by gold through a galvanic replacement reaction at the poly (dimethylsiloxane)/gold salt solution interface. It is demonstrated that, as a result of the galvanic replacement, the quasi-spherical silver nanoparticles uniformly distributed on the surface of the polymer are transformed into ribbon-like elongated gold aggregates. The formation of core-shell Ag-Au nanoparticles as an intermediate state of the low-temperature galvanic replacement is evidenced through microscopic and spectral methods. The collapse of this structure, in a later stage of the replacement, leads to the formation of elongated gold aggregates. The mechanism of the galvanic replacement under different conditions is investigated by closely following the evolution of the morphology, composition, and optical properties of the metal nanoparticles.
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