Glass Transition Temperature Of Poly Research Articles

Poly(propylene carbonate) Interpenetrating Cross-Linked Poly(ethylene glycol) Based Polymer Electrolyte for Solid-State Lithium Batteries

Solid polymer electrolyte based on semi-interpenetrating polymer network (s-IPN) was synthesized from the mixture of poly(propylene carbonate) (PPC), poly(ethylene glycol) methylether acrylate (PEGMEA), poly(ethylene glycol) diacrylate (PEGDA), and lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt via one-pot thermal curing method. The crosslinker PEGDA content and salt concentration were optimized. The ionic conductivity, lithium-ion transference number and electrochemical stability window of the s-IPN electrolyte were correlated with its thermal and physical properties. Differential scanning calorimetry measurements have shown a low degree of crystallinity in this s-IPN electrolyte. The electrolyte with higher salt concentration has lower ionic conductivity, consistent with higher glass transition temperature of poly(ethylene glycol) chain. The ionic conductivity was further enhanced by dispersion of lithium-ion conductive ceramic powder, lithium lanthanum zirconate (LLZO) into the s-IPN matrix. The optimized s-IPN has potential as a baseline material for future solid-state electrolyte designs.

Effects of Residual Solvent on Glass Transition Temperature of Poly(methyl methacrylate)

Effects of Residual Solvent on Glass Transition Temperature of Poly(methyl methacrylate)

Enhancement of the glass transition temperature of poly(methyl methacrylate) by salt

We investigated the effects of two metal salts, lithium trifluoromethanesulfonate (LiCF3SO3) and lithium bromide (LiBr), on the glass transition temperature (Tg) of poly(methyl methacrylate) (PMMA). Both LiCF3SO3 and LiBr greatly enhanced the Tg of PMMA under dry conditions. However, once the sample films were exposed to humidity, the PMMA containing LiCF3SO3 absorbed a large amount of water, which acts as a plasticizer. As a result, the Tg shifted to a lower temperature, which limits the utility of this polymer in industrial applications. In contrast, the Tg of PMMA containing LiBr was minimally affected by the absorption of water. This phenomenon can be explained by the ion–dipole interactions with the small number of dissociated lithium cations. Tg of PMMA was greatly enhanced by introducing ion–dipole interaction between lithium cations and carbonyl groups in PMMA as pseudo crosslinking points.

Synthesis, optical, and thermal properties of polyimides containing flexible ether linkage

ABSTRACTThe goal of this article was to synthesize a series of flexible polyimides containing ether linkage in main chain and clarified the effect of this ether linkage on some physical properties such as optical and thermal decomposition. Also, different functional group effects such as carbonyl (CO), hexa‐fluoro‐isopropylidene [C(CF3)2] and phenyl (C6H5) on these physical properties were evaluated. The structural characterization of poly(ether imide)s was performed using Fourier transform infrared, 1H‐nuclear magnetic resonance (NMR), and 13C‐NMR techniques. Optical band gap of polyimides was calculated in the range from 2.57 to 2.81 eV. Thermal characterization of poly(ether imide)s was carried out using thermogravimetry–differential thermal analysis and differential scanning calorimetry. Thermal stability of poly(ether imide)s was evaluated by initial decomposition temperature (Ton) and char. Ton value of polymers was determined in the range from 100 to 195 °C. In addition, glass transition temperatures of poly(ether imide)s were found between 144 and 148 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46573.

N,N-Dialkyl-3,5-difluorobenzenesulfonamides as a tool for tailoring the glass transition temperatures of poly(arylene ether)s

The use of the N,N-dialkylsulfonamide group as a tool for tailoring the glass transition temperature of poly(arylene ether)s was investigated. A series of N,N-dialkyl-3,5-difluorobenzenesulfonamides, in which the alkyl groups were varied from n-propyl to n-octyl, were prepared and converted to polymer form by meta activated nucleophilic aromatic substitution polycondensation reactions with bisphenol A. The polymers were fully characterized via size exclusion chromatography, NMR spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The resulting sulfonamide-based poly(arylene ether)s displayed moderate thermal stability with the onset of weight loss ranging from 369 to 410 °C. All of the materials were completely amorphous and the glass transition temperatures covered the range from 19 to 155 °C.

Effects of physicochemical properties of poly(lactide-co-glycolide) on drug release behavior of hydrophobic drug-loaded nanoparticles

Poly(lactide-co-glycolide) has been widely used and studied because of its biocompatibility and biodegradability. Many drug-loaded particles have been developed using this copolymer, however, information on its release behavior is lacking, especially for nanoparticles prepared using poly(l-lactide-co-glycolide). In this study, we used poly(dl-lactide-co-glycolide) (PLGA) and poly(l-lactide-co-glycolide) (PLLGA) with a 75/25 and 90/10 monomer composition of lactic acid/glycolic acid and molecular weights of 10,000. We determined the crystalline states, glass transition temperatures, and activation energies of the copolymers. Rifampicin-loaded PLGA7510, PLLGA7510, PLGA9010, or PLLGA9010 nanoparticles with 100-, 200- and 400-nm diameters were prepared, and in vitro release tests were carried out in phosphate-buffered saline at 37°C or 25°C for a week. The cumulative release ratio of rifampicin from nanoparticles using poly(l-lactide-co-glycolide) as a drug carrier was significantly lower than the release ratio from nanoparticles using poly(dl-lactide-co-glycolide), since the glass transition temperature of poly(l-lactide-co-glycolide) was 7°C higher than that of poly(dl-lactide-co-glycolide) at the same monomer composition. In addition, we found that the glass transition temperatures of the copolymers exerted a considerable influence on the initial release burst from the drug-loaded nanoparticles.

Topographically Flat Nanoplasmonic Sensor Chips for Biosensing and Materials Science.

Nanoplasmonic sensors typically comprise arrangements of noble metal nanoparticles on a dielectric support. Thus, they are intrinsically characterized by surface topography with corrugations at the 10-100 nm length scale. While irrelevant in some bio- and chemosensing applications, it is also to be expected that the surface topography significantly influences the interaction between solids, fluids, nanoparticles and (bio)molecules, and the nanoplasmonic sensor surface. To address this issue, we present a wafer-scale nanolithography-based fabrication approach for high-temperature compatible, chemically inert, topographically flat, and laterally homogeneous nanoplasmonic sensor chips. We demonstrate their sensing performance on three different examples, for which we also carry out a direct comparison with a traditional nanoplasmonic sensor with representative surface corrugation. Specifically, we (i) quantify the film-thickness dependence of the glass transition temperature in poly(methyl metacrylate) thin films, (ii) characterize the adsorption and specific binding kinetics of the avidin-biotinylated bovine serum albumin protein system, and (iii) analyze supported lipid bilayer formation on SiO2 surfaces.

Polymeric nanoparticles – Influence of the glass transition temperature on drug release

The physico-chemical characterisation of nanoparticles is often lacking the determination of the glass transition temperature, a well-known parameter for the pure polymer carrier. In the present study the influence of water on the glass transition temperature of poly (DL-lactic-co-glycolic acid) nanoparticles was assessed. In addition, flurbiprofen and mTHPP as model drugs were incorporated in poly (DL-lactic-co-glycolic acid), poly (DL-lactic acid), and poly (L-lactic acid) nanoparticles. For flurbiprofen-loaded nanoparticles a decrease in the glass transition temperature was observed while mTHPP exerted no influence on this parameter.Based on this observation, the release behaviour of the drug-loaded nanoparticles was investigated at different temperatures. For all preparations an initial burst release was measured that could be attributed to the drug adsorbed to the large nanoparticle surface. At temperatures above the glass transition temperature an instant drug release of the nanoparticles was observed, while at lower temperatures less drug was released. It could be shown that the glass transition temperature of drug loaded nanoparticles in suspension more than the corresponding temperature of the pure polymer is the pivotal parameter when characterising a nanostructured drug delivery system.

Predicting the Mechanical Properties of Organic Semiconductors Using Coarse-Grained Molecular Dynamics Simulations

The ability to predict the mechanical properties of organic semiconductors is of critical importance for roll-to-roll production and thermomechanical reliability of organic electronic devices. Here, we describe the use of coarse-grained molecular dynamics simulations to predict the density, tensile modulus, Poisson ratio, and glass transition temperature for poly(3-hexylthiophene) (P3HT) and its blend with C60. In particular, we show that the resolution of the coarse-grained model has a strong effect on the predicted properties. We find that a one-site model, in which each 3-hexylthiophene unit is represented by one coarse-grained bead, predicts significantly inaccurate values of density and tensile modulus. In contrast, a three-site model, with one coarse-grained bead for the thiophene ring and two for the hexyl chain, predicts values that are very close to experimental measurements (density = 0.955 g cm–3, tensile modulus = 1.23 GPa, Poisson ratio = 0.35, and glass transition temperature = 290 K). The m...

Effects of Polymer Tacticity and Molecular Weight on the Glass Transition Temperature of Poly(methyl methacrylate) Films on Silica

The glass transition temperature (Tg) of poly(methyl methacrylate) (PMMA) films supported by silica was studied as a function of film thickness at two molecular weights (MW = 2.5 and ∼50 kg/mol) and two syndiotacticities (s% = 56 and 69 or 79%). We found that the result depends on both the MW and s% in unconventional ways. For the 2.5 kg/mol films, the Tg was depressed for the lower s% films but enlarged for the higher s% films. For the ∼50 kg/mol films, however, the signs of the Tg change were reversed. To understand these observations, we constructed bilayer films from pairs of the studied PMMAs with roughly the same MW but different s%. Our result suggests that for the higher MW films, both the effects of the free surface and the substrate interface on the Tg are more significant on the higher s% PMMAs than on the lower s% PMMAs. For the lower MW films, however, the significance of the surface and substrate effects are modified, probably due to the effect of chain stiffness on the Tg and different degr...

Viscoelastic and dielectric properties of composites of poly(vinyl butyral) and alumina particles with a high filling degree

Filler–filler and filler–matrix interactions in polymer composites increase with filler concentration and strongly influence the mechanical and rheological properties of polymer composites. By means of the spouted bed spray granulation process polymer composites with an extremely high concentration of inorganic fillers can be prepared. In this work, the viscoelastic properties of highly filled composites of poly(vinyl butyral) (PVB) and alumina particles are studied in the glassy, entanglement and terminal flow regime of poly(vinyl butyral). Ceramic-polymer composites with a volume concentration of inorganic particles between 61 vol% and 77 vol% were prepared. Such large filler fractions imply a strong effect of filler–filler interactions on the viscoelastic properties of the composite. Dynamic-mechanical thermal analysis reveals that the composites are characterized by a predominantly elastic behaviour below and above the glass transition temperature of the polymer phase because of strongly pronounced filler–filler and polymer–filler interactions. A phenomenological equation is proposed in order to describe the reinforcement effect which implies an increase of storage modulus by a factor of up to four orders of magnitude. The results of frequency and strain sweeps in the oscillatory mode show that the polymer phase strongly influences the deformation of the contact network of inorganic particles. Differential scanning calorimetry and broadband dielectric spectroscopy indicate that the glass transition temperature of poly(vinyl butyral) does not significantly differ within experimental resolution for pristine PVB and the PVB phase in the composites.

Evaluation of glass transition temperature of PVC/POSS nanocomposites

Abstract The poly(vinyl chloride) was modified by polyhedral oligomeric silsesquioxane with 3-chloropropyl groups (CP–POSS) by POSS concentration between 0.5 and 5 wt%. Two methods of POSS incorporation were applied, i.e. direct solid powders mixing or addition of POSS to PVC solution in THF. The final samples were produced by melt mixing in the Brabender mixer chamber. By means of the glass transition temperature (T g ) determination the influence of a low contain of CP–POSS on the effect of plasticization of the PVC compounds was investigated. Depending on the measurements method (dynamic mechanical analysis DMA and differential scanning calorimetry DSC) and on the DMA measurement frequency various values of the T g were observed. It was found that CP–POSS may act as a plasticizer, leading to certain lowering of the glass transition temperature of poly(vinyl chloride).

Molecular motion and relaxation below glass transition temperature in poly (methyl methacrylate) studied by positron annihilation

In this paper, we present the study of local molecular motions in poly (methyl methacrylate) (PMMA) below glass transition temperature by measuring the ortho-positronium (o-Ps) intensity. Two series of experiments were performed: (1) the PMMA sample was irradiated by 22Na positron source with elongated time at room temperature, 225 K and 16 K, respectively, and positron lifetime spectra were measured as a function of irradiation time and (2) Positron lifetime and Doppler broadening spectra were measured as a function of temperature from 16 to 350 K after positron irradiation at 16 K for more than 350 h. While the o-Ps lifetime always shows no change with elapsed time, decrease and increase of o-Ps intensity I3 are observed at 225 K and 16 K, which are interpreted as the result of positron irradiation-induced free radicals and trapped electrons, respectively. With temperature increasing from 16 K, there is a continuous drop of I3 beginning at around 100 K. This is due to some local group movements such as the ester and main chain methyl group rotations, which lead to the detrapping of accumulated electrons. These local motions do not need additional free volume, so we observed no change of the o-Ps lifetime. Some other structural relaxations such as β-relaxation are also observed and discussed.

Experimental Study of the Synergistic Plasticizing Effect of Carbon Dioxide and Ibuprofen on the Glass Transition Temperature of Poly(methyl methacrylate)

The solubility of small molecules in a polymer and the consequent glass transition temperature reduction of the polymer with a plasticizing effect are two of the most important thermodynamic properties of small molecule–polymer systems. In this study, with an improved dual QCM device and corresponding method for determination, the solubilities of CO2 in poly(methyl methacrylate) (PMMA) film, ibuprofen (IBU) in supercritical carbon dioxide (SCCO2), and the CO2/IBU compound into PMMA film at different temperatures and pressures were determined, respectively, and then the solubility of IBU in PMMA film was calculated according to the theory of infinite dilute solution. Both CO2 and IBU molecules can plasticize the polymer in CO2–polymer and drug–polymer systems. For the CO2–IBU–PMMA ternary system, the glass transition temperature reduction behavior of PMMA versus the pressure of CO2 and proportion of IBU in PMMA was investigated, which would illustrate the synergistic plasticizing effect of CO2 and IBU on the glass transition temperature of PMMA.

Determination of thermodynamic properties of poly (cyclohexyl methacrylate) by inverse gas chromatography.

In this work, some thermodynamic properties of poly (cyclohexyl methacrylate) were studied by inverse gas chromatography (IGC). For this purpose, the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times (t(r)) of the probes were determined from the interactions of poly (cyclohexyl methacrylate) with n-pentane, n-hexane, n-heptane, n-octane, n-decane, methanol, ethanol, 2-propanol, butanol, acetone, ethyl methyl ketone, benzene, toluene and o-xylene by IGC technique. Then, the specific volume (Vg(0)) was determined for each probe molecule. By using (1/T; lnVg(0)) graphics, the glass transition temperature of poly (cyclohexyl methacrylate) was found to be 373 K. The adsorption heat under the glass transition temperature (deltaH(a)), and partial molar heat of sorption above the glass transition (deltaH1(S)), partial molar free energy of sorption (deltaG1(S)) and partial molar entropy of sorption (deltaS1(S)) belonging to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution (deltaH1(infinity)), partial molar free energy of mixing at infinite dilution (deltaG1(infinity)), Flory-Huggins interaction parameter (chi12(infinity)) and weight fraction activity coefficient (a1/w1)(infinity) values of polymer-solute systems were calculated at different column temperatures. The solubility parameters (delta2) of the polymer were obtained by IGC technique.

Double Glass Transition Temperatures of Poly(methyl methacrylate) Confined in Alumina Nanotube Templates

Recently, confinement of polymers with different geometries has become a research hotspot. Here, we report the dramatic deviation of glass transition behaviors of poly(methyl methacrylate) (PMMA) confined in cylindrical nanopores with diameter significantly larger than chain’s radius of gyration (Rg). Fast cooling a PMMA melt in the nanopores results in a glass with one single glass transition temperature (Tg). But two distinct Tgs are detected after slow cooling the melt. The deviation in Tg could be as large as 45 K. This phenomenon is interpreted by a two-layer model. During vitrification under slow cooling two distinct layers are formed: a strongly constrained interfacial layer showing an increased Tg as compared to that of the bulk polymer and a core with a decreased Tg. By thermal annealing experiments, we find that these two Tgs are inherently correlated. In addition, the deviation of Tg for PMMA confined in nanopores reveals a dependence on molecular weight.

Oscillatory shear induced gelation of graphene–poly(vinyl alcohol) composite hydrogels and rheological premonitor of ultra-light aerogels

Time evolution of 3-D structure of GO hydrogels was explored by rheological measurements. We showed that the GO hydrogels were thickened drastically by oscillatory shear flow if and only if both the angular frequencies and shear strain are small. We also showed that the plateau modulus (GN′) of GO hydrogels is rheological premonitory of ultra-light aerogels. The ultra-light aerogel fabricated in this work exhibited low density of 4.0 mg/cm3, low surface resistivity of 6.6 Ω/sq, high specific area of 1069 m2/g, and high recoverable strain of 94% in compression. The glass transition temperature of poly(vinyl alcohol) (PVA) in the aerogel was 49 K higher than that of pure PVA. The thermal stability of the GO/PVA aerogel in air environment was superior to that of dried GO in itself in thermogravimetric analysis (TGA).

Where is the glass transition temperature of poly(tetrafluoroethylene)? A new approach by dynamic rheometry and mechanical tests

Polytetrafluoroethylene (PTFE) has been used for many years in different application fields due to its outstanding chemical and physical properties. But, the value of its glass transition temperature is still today a matter of controversy and very different values are proposed in the literature. This paper proposes to answer to this scientific question using dynamic mechanical measurements. First, the viscoelastic properties of PTFE are described on a large temperature range and the influence of the shearing frequency is carefully investigated. Then, the effects produced by the polymer annealing on its thermomechanical behavior are detailed. This study comforts the idea that PTFE amorphous phase should be considered as comprised of two distinct regions. The first one named “mobile amorphous fraction” (MAF) is able to relax at low temperature (T=−103°C). The other one is specific of the macromolecular segments present at the boundaries between crystalline and amorphous domains. Due to the close vicinity of the crystallites, these macromolecular segments present a more restricted mobility. The corresponding phase is designated as the “rigid amorphous fraction” (RAF) and its mechanical relaxation produces itself at higher temperature (T=116°C). Actually, this latter value is strongly dependent on the material crystallinity degree. In particular, it is shifted to higher temperature after occurrence of a recrystallization that is accompanied by a further reduction of the RAF’s dynamic. Instead, the characteristics of the MAF relaxation are poorly affected. Tensile tests also support that the “real” Tg of the polymer is located at low temperature. All these results have been compared to those of the literature to propose a real scientific discussion and to understand the origin of somewhat contradictory interpretations.

Imidazole Polymers Derived from Ionic Liquid 4-Vinylimidazolium Monomers: Their Synthesis and Thermal and Dielectric Properties

The synthesis of 1-ethyl-3-methyl-4-vinylimidazolium triflate, its polymerization, and ion exchange to yield a family of 4-imidazolium polymers with a variety of anions are described. For comparative purposes, the synthesis, polymerization, and ion exchange of an analogous set of 1-vinylimidazolium polymers are also presented. The comparative thermal and dielectric characteristics of the 4-vinyl- and 1-vinylimidazolium salts were evaluated. The trends in the glass transition (Tg) characteristics of the various 4-vinylimidazolium and 1-vinylimidazolium polymers were similar; however, the glass transition temperatures of poly(4-vinylimidazolium) BF4–, PF6–, AsF6–, and CF3SO3– salts were significantly higher than those of the corresponding poly(1-vinylimidazolium) salts. This difference and the increase in Tg in going from BF4– to AsF6– in the 4-vinylimidazolium series were attributed to enhanced intramolecular bridging between imidazolium moieties positioned 1,3 or 1,5 along the polymer chain. In the dielec...

The glass transition temperature of poly(phenylene sulfide) with various crystallinities

AbstractThe glass transition temperature (Tg) of poly(phenylene sulfide) (PPS) with various crystalline fractions has been studied using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The DSC measurements show that Tg can be observed from the heating curves for the PPS sample with very low crystallinity, and no Tg is observed when the crystallinity is over 8%. DMA indicates that crystallinity has an important effect on molecular chain segment motion of PPS. When the crystallinity, Xc, of PPS is over 38%, there is only one chain segment motion, which mainly results from the crystalline chain vibration; while three different chain segment motions occur for PPS samples with lower crystallinity (Xc < 26%), which are amorphous chain segment motion, crystalline chain segment motion and constrained amorphous chain segment motion. Tg of PPS is mainly caused by the amorphous chain segment motion which is independent of the crystallinity, while the relaxation temperature corresponding to crystalline chain motion shifts to lower temperature as the crystallinity increases. The reduction of the relaxation temperature can be attributed to the disorder‐order transition of amorphous chains for PPS with lower crystallinity. © 2012 Society of Chemical Industry