Glass Transition Temperature Of Poly Research Articles

Evidence of glass transition in thin films of maleic anhydride derivatives: Effect of the surfactant coadsorption

The glass transition temperature of poly (maleic anhydride-alt-1-octadecen) and poly (styrene-co-maleic anhydride) cumene-terminated thin films has been measured by mechanical relaxation of Langmuir films of these polymers. The dynamical properties show glass-like features (non-Arrhenius relaxation times and non-Debye mechanical response) interpreted by the coupling model. The glass transition temperature values determined by a mechanical relaxation experiment (step-compression) agree very well with those obtained by surface potential measurements. It is found that the glass transition temperature values in thin films decrease by about 100 K as compared with those corresponding to the bulk polymers. The coadsorption of the water-insoluble surfactant DODAB decreases the glass transition temperature.

Uniaxial Stretching above the Glass Transition Temperature of Poly(Ethylene Terephthalate) and its Effects on the Structure Development

This work deals with an experimental investigation of the strain-induced crystalline microstructure that develops under uniaxial elongation of amorphous poly(ethylene terephthalate), PET, above its glass transition temperature, as an approach for industrial stretch-blow moulding processes. The present study aims at: a) defining the most relevant processing parameters which govern and are of significance for the induced morphology, and b) establishing of relationships between processing and morphology. Compression moulded amorphous PET was uniaxial stretched with variations of following stretching parameters: stretching temperature, Tst, stretching velocity, Vst, and stretching ratio, λst, that were varied in two levels according to a L8 Taguchi orthogonal array. The developed morphologies were characterized by differential scanning calorimetry (DSC) and birefringence measurements. Obtained results were analyzed by ANOVA statistical tool. The glass transition temperature, Tg, is influenced mainly by the stretching ratio. The cold crystallization temperature, Tcc, is determined by complex influence of all stretching variables and the interaction Tstxλst. The degree of crystallinity, χc, mainly depends upon Vst and Tstxλst interaction. The birefringence, n, is essentially determined by λst and the interaction Vstxλst. The distinct morphological parameters are then related with the purpose of understand the structure development upon polymer stretching.

Preparation and characterization of poly(MMA-M12-BPMA)/TiO2 composite particles

In this paper, poly(MMA-M12-BPMA)/TiO2 composite particles were prepared by the copolymerization of a reactive surfactant sodium sulfopropyl-laurylmaleate (M12) and a reactive UV-stabilizer 2-hydroxy-4-(3-methacryloxy-2-hydroxylpropoxy) benzophenone (BPMA) with methyl methacrylate (MMA) in the presence of TiO2. The structure and performance of composite particles were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, gel permeation chromatography, ultraviolet–visible absorption spectroscopy, differential scanning calorimeter, and scanning electron microscope.The measurement results indicate that the percentage of grafting and the grafting efficiency can reach 336.87% and 36.38%, respectively, and the glass transition temperature of poly(MMA-M12-BPMA)/TiO2 composite particles is higher than that of poly(MMA-M12-BPMA); the size of the composite particles is about 130–200 nm. The poly(MMA-M12-BPMA) grafted from the surface of TiO2 keeps the excellent characteristic of BPMA that possesses high absorbance of ultraviolet light, which is very important for improving UV-resistant performance of the polymethyl methacrylate. These research results are very useful for preparing polymethyl methacrylate with resistance to UV light.

Cyclohexyl-Substituted Polyglycolides with High Glass Transition Temperatures

The substituted glycolides rac-dicyclohexylglycolide (rac-3,6-dicyclohexyl-1,4-dioxane-2,5-dione), meso-dicyclohexylglycolide, R,R-dicyclohexylglycolide, and rac-methylcyclohexylglycolide (rac-3-cyclohexyl-6-methyl-1,4-dioxane-2,5-dione) have been synthesized, and both solution and bulk polymerizations of these monomers are reported. The polymerization kinetics of these new monomers were studied and compared to data for rac-diisopropylglycolide (rac-3,6-diisopropyl-1,4-dioxane-2,5-dione) and rac-lactide. The solution polymerization rates followed the order: rac-dicyclohexylglycolide < rac-diisopropylglycolide < rac-methylcyclohexylglycolide < rac-lactide. The glass transition temperature of poly(rac-dicyclohexylglycolide) is 98 °C, consistent with a stiff polyglycolide backbone. meso-Dicyclohexylglycolide and R,R-dicyclohexylglycolide were synthesized and polymerized to study the effect of stereochemistry on the polymer properties. The glass transition temperature of meso-dicyclohexylglycolide was 96 °C,...

Synthesis and characterization of poly(amideimide)s containing pendent flexible alkoxy chains

A series of aromatic diacylhydrazides containing pendent flexible alkoxy chains, viz., 5-butyloxyisophthalicacid dihydrazide, 5-octyloxyisophthalicacid dihydrazide, 5-dodecyloxyisophthalicacid dihydrazide and 5-hexadecyloxyisophthalicacid dihydrazide were synthesized by the hydrazinolysis reaction of the corresponding aromatic esters with hydrazine hydrate. Diacylhydrazides were each polycondensed with aromatic dianhydrides, viz., 4,4′-oxydiphthalic anhydride (ODPA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) to obtain new poly(amideimide)s. Poly(amideimide)s had inherent viscosity in the range 0.55–0.88 dL/g in N, N-dimethylacetamide (DMAc) at 30 ± 0.1 °C. Poly(amideimide)s were found to be soluble in DMAc, N, N-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP) and pyridine and could be cast into tough, flexible and transparent films from a solution in DMAc. X-ray diffractograms revealed that poly(amideimide)s with longer alkoxy chains had layered structures. Glass transition temperature of poly(amideimide)s containing pendent flexible alkoxy chains were in the range 215–245 °C. Temperature at 10% weight loss was in the range 380–410 °C in nitrogen atmosphere indicating good thermal stability of poly(amideimide)s.

Application of Sample—Sample Two-Dimensional Correlation Spectroscopy to Determine the Glass Transition Temperature of Poly(Ethylene Terephthalate) Thin Films

The glass transition temperatures (Tg) of poly(ethylene terephthalate) (PET) thin films with different thicknesses are determined by analyzing their in situ reflection-absorption infrared (RAIR) spectra measured over a temperature range of 28 to 84 degrees C. The criterion of standard deviation of the covariance matrices is used as a graphical indicator for the determination of the Tg present in the sample-sample two-dimensional (2D) correlation spectra calculated from the temperature-dependent RAIR spectra. After two data pretreatments of the first derivative of the spectral absorbance versus temperature and the mean normalization over the wavenumbers are sequentially carried out on the RAIR spectra, an abrupt change of the first-derivative correlation spectra with respect to temperature is quickly obtained. It reflects the temperature at which the apparent intensity changes in pertinent absorption bands of PET thin films take place due to the dramatic segmental motion of PET chain conformation. The Tg of the thin PET films is accordingly determined. The results reveal that it decreases with a great dependence on the film thickness and that sample-sample 2D correlation spectroscopy enables one to determine the transition temperature of polymer thin films in an easy and valid way.

Size and pressure effects on glass transition temperature of poly (methyl methacrylate) thin films

A simple and unified model, without any adjustable parameter, is developed for size and pressure effects on glass transition temperatures of nanopolymers. The model is based on a model for size dependent glass transition temperature of nanopolymer glasses under ambient pressure, and a pressure-dependent function of the root of mean-square displacement of atom vibration. It is found that the size- and pressure-dependent glass transition temperatures of free-standing films or supported films having weak interaction with substrates decreases with decreasing of pressure and size. However, the glass transition temperature of supported films having strong interaction with substrates increases with the increase of pressure and the decrease of size. The predicted results correspond with available experimental evidences for atactic-Poly (methyl methacrylate) thin films under hydrostatic pressure or under the pressure induced by supercritical fluid CO2. In addition, the predicted glass transition temperature of isotactic-Poly (methyl methacrylate) thin films under ambient pressure is consistent with available experimental evidences.

N,N-dicyclohexylcarbodiimide assisted synthesis and characterization of poly(vinyl alcohol- co-vinyl levulinate)

Poly(vinyl alcohol- co-vinyl levulinate) was synthesized by N,N-dicyclohexylcarbodiimide assisted esterification of poly(vinyl alcohol) with free levulinic acid using 4-pyrrolidino pyridine as a catalyst in N,N-dimethyl acetamide/lithium chloride solvent system in order to optimize the reaction condition. The vinyl levulinate content in the copolymer was attained up to 0.95. The 13C NMR dyad compositional analysis indicated the block character of the copolymer was 0.92, suggesting almost random poly(vinyl alcohol- co-vinyl levulinate) was formed. Glass transition temperature dependence on vinyl levulinate content of the copolymers fitted better into Gordon–Taylor equation as compared with Fox equation and the glass transition temperature of poly(vinyl levulinate) was given as 2.3 °C by the least regression method.

Synthesis, properties and controlled release behaviors of hydrogel networks using cyclodextrin as pendant groups

Based on inclusion character of β-cyclodextrin ( β-CD) with drug molecule and low glass transition temperature of poly(2-hydroxyethyl acrylate) (PHEA), a series of hydrogels with different compositions were synthesized by the copolymerization of a monovinyl cyclodexrin monomer with 2-hydroxyethyl acrylate (HEA). The structure and properties of the hydrogels were characterized by FTIR, DSC, TGA and swelling measurements. It is found that swelling ratios of these β-CD hydrogels can keep a relative stability in the range of pH from 1.4 to 7.4, and are not sensitive to change in NaCl concentration. Using drug N-acety-5-methoxytryptamine (melatonin, MEL) as a model molecule, the controlled drug release behaviors of these hydrogels were investigated. The results indicate that the diffusion and permeation of MEL from the hydrogels may be a dominant factor for its release. Owing to the formation of MEL/ β-CD retarding diffusion rate of MEL, a sustained release of MEL from hydrogel with high content of β-CD can be obtained compared with hydrogel PHEA without β-CD.

Radical copolymerization of vinylidene fluoride with perfluoroalkylvinyl ethers

The radical copolymerization of perfluoromethylvinyl ether (PMVE) and perfluoropropylvinyl ether (PPVE) with vinylidene fluoride (VDF), initiated by tertiobutyl peroxypivalate (TBPPI) and di tertiobutyl peroxide (DTBP), respectively, are presented. The kinetics of copolymerization were investigated for each monomer from series of at least eight reactions for which the initial [VDF] 0/[fluorinated vinyl ether] 0 molar ratios ranged between 20/80 and 80/20. The copolymer compositions of these random-type copolymers were calculated by means of 19F NMR spectroscopy and allowed one to quantify the respective amounts of each monomeric unit in the copolymer. According to the Tidwell and Mortimer method, the reactivity ratios ( r i ) of both comonomers for each type of copolymerization were obtained : r VDF = 3.40 ± 0.40 and r PMVE = 0 at 74 °C; and r VDF = 1.15 ± 0.36 and r PPVE = 0 at 120 °C. Moreover, the glass transition temperatures ( T g’s) of poly(VDF-co-PMVE) and poly(VDF-co-PPVE) copolymers containing different amounts of VDF and PMVE or PPVE, were determined and the theoretical glass transition temperatures of poly(PMVE) and poly(PPVE) homopolymer were deduced.

Synthesis of methyl methacrylate and N‐aryl itaconimide block copolymers via atom‐transfer radical polymerization

AbstractThe paper describes the synthesis of block copolymers of methyl methacrylate (MMA) and N‐aryl itaconimides using atom‐transfer radical polymerization (ATRP) via a poly(methyl methacrylate)–Cl/CuBr/bipyridine initiating system or a reverse ATRP AIBN/FeCl3·6H2O/PPh3 initiating system. Poly(methyl methacrylate) (PMMA) macroinitiator, ie with a chlorine chain‐end (PMMA‐Cl), having a predetermined molecular weight (Mn = 1.27 × 104 g mol−1) and narrow polydispersity index (PDI = 1.29) was prepared using AIBN/FeCl3·6H2O/PPh3, which was then used to polymerize N‐aryl itaconimides. Increase in molecular weight with little effect on polydispersity was observed on polymerization of N‐aryl itaconimides using the PMMA‐Cl/CuBr/Bpy initiating system. Only oligomeric blocks of N‐aryl itaconimides could be incorporated in the PMMA backbone. High molecular weight copolymer with a narrow PDI (1.43) could be prepared using tosyl chloride (TsCl) as an initiator and CuBr/bipyridine as catalyst when a mixture of MMA and N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 was used. Thermal characterization was performed using differential scanning calorimetry (DSC) and dynamic thermogravimetry. DSC traces of the block copolymers showed two shifts in base‐line in some of the block copolymers; the first transition corresponds to the glass transition temperature of PMMA and second transition corresponds to the glass transition temperature of poly(N‐aryl itaconimides). A copolymer obtained by taking a mixture of monomers ie MMA:N‐(p‐chlorophenyl) itaconimide in the molar ratio of 0.83:0.17 showed a single glass transition temperature. Copyright © 2005 Society of Chemical Industry

Supercritical carbon dioxide foaming of elastomer/heterocyclic methacrylate blends as scaffolds for tissue engineering

This study reports on the supercritical carbon dioxide (scCO2) foaming of rubber toughened heterocyclic methacrylates for potential applications as non-degradable scaffolds in tissue repair and engineering. Porous blends of styrene–isoprene–styrene copolymer elastomer (SIS) and tetrahydrofurfuryl methacrylate (THFMA) at three SIS/THFMA compositions that ranged from methacrylate to elastomer rich were foamed and characterised in terms of their morphological, mechanical and biological properties. The results showed that the foaming factor (FF) was dependent on blend composition and the foaming conditions demonstrating that the process was tuneable. A greater FF, resulting in higher open and total porosities, was obtained for THFMA rich formulations, which were demonstrated by a predominantly open pore structure. Quasi-static and dynamic mechanical analysis (DMA) showed that the foamed SIS/THFMA blends gave distinct behaviours according to their compositions which were in the range of mechanical properties of soft tissues. The loss modulus and mechanical loss tangent through DMA gave two transition regions associated with the glass transition temperatures of poly(THFMA) and polystyrene components in the blends, along with a reduction in storage modulus. Cell adhesion and spreading in terms of neuroblastoma (human neuron-like SH-SY5Y) cells and ovine meniscal chondrocytes were demonstrated for scaffolds with THFMA rich formulations confirming their suitability for tissue engineering.

Synthesis, characterization and photocrosslinking properties of polyacrylamides having bromo substituted pendant cinnamoyl moieties

New 3- and 4-bromocinnamoyl aniline were synthesized condensing 4-aminoacetophenone and the respective bromobenzaldehydes in the presence of sodium hydroxide. The monomers, 4-(3′-bromocinnamoyl) phenyl acrylamide (4,3′-BCPA) and 4-(4′-bromocinnamoyl) phenyl acrylamide (4,4′-BCPA) were prepared by reacting the respective chalcones and acryloyl chloride in the presence of triethylamine at 0–5 °C. Homopolymers of 4,3′-BCPA and 4,4′-BCPA was carried out in methyl ethyl ketone using benzoyl peroxide (BPO) under nitrogen atmosphere at 70 °C. The prepared polymers were characterized by UV, IR, 1H-NMR and 13C-NMR techniques. The molecular weights ( M w and M n) of the polymers were determined by gel permeation chromatography. The thermogravimetric analysis (TGA) of the polymers in nitrogen atmosphere reveals that they possess very good thermal stability required of a negative type photoresist. The glass transition temperature of poly(4,3′-BCPA) and poly (4,4′-BCPA) were found to be 55 and 64 °C respectively. The solubility of the polymers was tested in various polar and non-polar solvents. Photocrosslinking nature of the polymer samples was carried out in the presence and absence of various triplet photosensitizers in solution phase using chloroform solvent under medium frequency UV light. For using the polymers as negative photoresist materials the rate of photocrosslinking of the polymers was measured under the influence of different solvents, concentrations and position of the substituent.

Glass Transition Temperature Determination of Poly(ethylene terephthalate) Thin Films Using Reflection−Absorption FTIR

By using the in-situ reflection−absorption infrared technique, the glass transition temperatures of poly(ethylene terephthalate) thin films were determined by detecting the abrupt change in the absorbance ratio of two comparable bands at 1340 cm-1 (trans conformation) and 1370 cm-1 (gauche conformation) during heating. It was found that the Tg of thin PET films reduces with respect to that of bulk sample and has a great dependence on the film thickness. The conformational energy difference (ΔE) between trans and gauche states of each film was also calculated. The results indicate that the thickness dependence of calculated ΔE is nearly consistent with that of Tg measured. Furthermore, the relaxation behavior of the PET chains in thin films prepared by spin-coating and the influence of annealing on the Tg measured were also investigated.

Facile synthesis of poly(4‐hydroxy styrene) from polystyrene

AbstractA facile methodology to modify polystyrene, to incorporate alkali soluble hydroxy groups, is reported. Polystyrene of well‐defined number‐average molecular weights in the range of 3000 to 50,000 were prepared by suspension polymerization at 80°C by varying the relative mole ratio of carbon tetrachloride, used as chain transfer agent. Polystyrenes were acetylated; the acetyl groups were converted to acetoxy groups, by Baeyer–Villiger oxidation, and hydrolyzed in a nonaqueous alkaline medium to generate hydroxy groups. The extents of modifications were monitored by infrared spectroscopy. The glass transition temperatures of poly(4‐acetylstyrene‐co‐styrene), poly(4‐acetylstyrene‐co‐4‐acetoxystyrene‐co‐styrene), and poly(4‐hydroxystyrene‐co‐4‐acetylstyrene‐co‐styrene) were 107, 134, and 142°C, respectively. The polymers were evaluated in photoresist formulations. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3192–3201, 2004

Micromechanical Behavior and Glass Transition Temperature of Poly(Methyl Methacrylate)–Rubber Blends

The microhardness of transparent rubber‐toughened poly(methyl methacrylate) (RTPMMA) was investigated by means of the microindentation technique. Core‐shell particles (CSP) with a rubbery shell were used as reinforcing material for the production of RTPMMA. The increasing volume fraction of CSP within the poly(methyl methacrylate) (PMMA) matrix is shown to soften the material, diminishing the hardness (H) value of RTPMMA of about 40% of the initial value at 35 vol% CSP content. Creep experiments under the indenter are reported. The creep constant is found to increase by adding CSP up to a leveling‐off value. On the other hand, the thermal variation of the creep constant for the blends shows a maximum. Results reveal a good correlation of the glass transition temperature (T g) value deduced from microindentation, and the values obtained from differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques. Contrary to expectation H is shown to decrease with increasing glass transition temperature. In the case of the drawn materials, the indentation anisotropy is shown to gradually increase with draw ratio and CSP content. This finding is explained on the basis of the higher orientation of the PMMA molecules near the periphery of CSP.

Relationships between the Glass Transition Temperatures and the Type of Cations in Poly(ethyl acrylate) Ionomers

Glass transition temperatures of poly(ethyl acrylate) ionomers neutralized with various cations were studied dynamic mechanically in terms of ion content and the type of cations. On one hand, it was found that with increasing ion content the matrix Tgs increased linearly and identically regardless of the variety of cations. Thus, it is inferred that the type of cations did not affect the matrix Tgs. On the other hand, in the plots of the cluster Tgs vs (ion content × charge)/(distance between charges), it was observed that the cluster Tgs were superimposed on the straight line. This result implies that the cluster Tg involving ion hopping is affected by the type of cations. It was also found that the ionic modulus did not change with the type of cations significantly. In addition, the small-angle X-ray study showed that with increasing the radius of a cation the distance between scattering centers increased. Thus, it was postulated that the restricted mobility layer became thicker slightly with the increasing size of a cation.

Synthesis and photophysical properties of alternating copolymers containing triphenylamine moieties

AbstractTwo alternating copolymers containing triphenylamine and biphenyl or fluorene, poly[triphenylamine‐alt‐biphenylene vinylene] (TPA‐PBPV) and poly[triphenylamine‐alt‐2,7‐fluorenenylene vinylene] (TPA‐FLV) were synthesized by means of the Wittig reaction. Both the polymers show good solubility in common organic solvents and excellent film‐forming ability. Thermogravimetric analysis investigation demonstrates that the polymers have high thermal stability, the degradation temperature of TPA‐FLV is as high as 499.0 °C. Differential scanning calorimetry results indicate that the glass transition temperature of poly TPA‐FLV is higher than 200 °C, much higher than that of PBPV‐TPA, which might be a merit for the long‐life operation of light‐emitting devices. The photophysical properties of the polymers were investigated in both CH2Cl2 solution and spin‐coated film, photoluminescence efficiencies are also determined, PFV‐TPA has a higher efficiency, which may make it a more promising candidate for light‐emitting materials. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Thermoreversible Poly(alkyl acrylates) Consisting of Self-Complementary Multiple Hydrogen Bonding

The synthesis and characterization of novel self-complementary multiple hydrogen-bonded (SCMHB) polymers containing pendant 2-ureido-4[1H]-pyrimidone (UPy) units are described. SCMHB pendant polymers, poly(butyl acrylate-co-SCMHB methacrylate), were prepared via free radical copolymerization of butyl acrylate (BA) and a novel SCMHB methacrylate (SCMHB MA) monomer, which was synthesized via a quantitative coupling reaction between 2-isocyanatoethyl methacrylate (ICEMA) and methyl isocytosine (MIS) in DMSO. The glass transition temperatures of poly(BA-co-SCMHB MA) increased in a linear fashion as the SCMHB MA content increased. Thermogravimetric analysis of the copolymers exhibited an onset of weight loss at 217 °C. Solution viscosity analysis indicated that SCMHB pendant polymers strongly aggregated in nonpolar solvents, such as toluene and CHCl3, and dissociated in polar solvents, such as THF. Based on melt rheological characterization, the melt viscosity of soluble SCMHB pendant polymers was an order of magnitude higher than that of PBA due to strong aggregation in the melt state. SCMHB pendant polymers exhibited thermoreversible characteristics, and complete dissociation in the melt state was observed at 80 °C, which was consistent with our earlier studies involving SCMHB-terminated poly(styrene) (PS), poly(isoprene) (PI), and PS-b-PI block copolymers. In addition, SCMHB units completely dissociated at 80 °C in toluene on the basis of 1H NMR measurements. The 90° peel strength values for SCMHB-containing polymers increased as the SCMHB units increased due to the strong interaction of SCMHB units with the glass surface. Thin-layer chromatography indicated that the interaction of SCMHB pendant polymers with silica was more favorable compared to PBA homopolymer.

ポリ（アルコキシメチルアクリルアミド）の接着表面処理剤への応用

Two series of copolymers, Poly (RAAm-co-ST) and Poly (BMAAm-co-R'MA), as the novel primers in adhesive bonding polypropylene (PP) were prepared by radical copolymerization of alkoxymethyl acrylamide (RAAm) and styrene (ST) or alkyl methacrylate (R'MA). Alkoxy groups (OR) in the RAAm moieties used were methoxy, ethoxy, isobutoxy and butoxy, whereas alkyl groups (R') in the R'MA moieties were methyl, ethyl, isopropyl, isobutyl, n-butyl and n-hexyl. Homopolymer of RAAm, Poly (RAAm), was also prepared and characterized: the glass transition temperature of Poly (RAAm) was Tg=76.8-70.0°C and Poly (RAAm) was thermally decomposed through a two step degradation with the evolution of corresponding alcohol. The bonding properties of PP, using two series of copolymers as primers, were studied by measuring the shear strength (τ) of single-lap joints between PP and PP or other substrates such as polyethyleneterephthalate (PET), nylon 66 (66N), alminium, steel and glass. The primers tested were effective when used with polyurethane adhesive. Mixed substrate bonds prepared between PP and others gave substantial bond strength (τ=48.4-51.3MPa) in comparison to bond strength for unprimered controls (τ=8.9-16.7MPa). Maximum bond strength was obtained when Poly (BMAAm-co-HMA) was chosen as a primer. The mechanism for the adhesive bonding of PP was discussed.