Significant glass-transition-temperature increase through hydrogen-bonded copolymers (original) (raw)
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Polymer, 2003
A series of poly(vinylphenol-co-vinylpyrrolidone) (PVPh-co-PVP) copolymers were prepared by free radical copolymerization of acetoxystyrene with vinylpyrrolidone (PAS-co-PVP), followed by selective removal of the acetyl protective group. These copolymers were investigated by solid state nuclear magnetic resonance (NMR) and thermal gravimetric analyzer (TGA) to compare with previous results on differential scanning calorimetry (DSC) and Fourier-Transform infrared spectroscopy (FTIR) analyses. The spin-lattice relaxation time in the rotating frame ðT 1r ðHÞÞ of the PVPh-co-PVP is greater than the corresponding PVPh/PVP blend, indicating that the polymer mobility is more restricted and high rigid character of the former. At the same time, the thermal decomposition temperature of homopolymer, copolymer and polymer blend is the order of PVPh-co-PVP copolymer. PVPh/PVP blend. pure PVP homopolymer. PAS-co-PVP copolymer and this order is consistent with previous studies on DSC, FTIR and NMR analyses. In order to understand the mechanism of significant glass transition temperature increase of the PVPh-co-PVP copolymer, the degree of hydrolysis was controlled by varying time of reaction of the PAS-co-PVP copolymer.
Thermal behavior and specific interaction in high glass transition temperature PMMA copolymer
Polymer, 2003
A series of high glass transition temperature copolymers based on poly(methyl methacrylate) (PMMA) were prepared by free radical copolymerization of methacrylamide and methyl methacrylate monomers in dioxane solvent. The thermal properties and hydrogen-bonding interactions of these poly(methacrylamide-co-methyl methacrylate) (PMAAM-co-PMMA) copolymers with various compositions were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and solid-state nuclear magnetic resonance (NMR) spectroscopy. A large positive deviation in the behavior of T g ; based on the Kwei equation from DSC analyses, indicates that strong hydrogen bonding exists between these two monomer segments. The FTIR and solid-state NMR spectroscopic analyses give positive evidence for the hydrogen-bonding interaction between the carbonyl group of PMMA and the amide group of PMAAM (e.g. by displaying significant changes in chemical shifts). Furthermore, the proton spin-lattice relaxation time in the rotating frame ðT 1r ðHÞÞ has one single value over the entire range of compositions of copolymers, and gives a value shorter than the average predicted. The proton relaxation behavior indicates the rigid nature of the copolymer.
2003
The thermal property and hydrogen bonding in polymer blends of poly(vinylphenol) (PVPh) and poly(hydroxylether of bisphenol A) (phenoxy) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR). This PVPh/phenoxy blend shows single compositiondependent glass transition temperature over the entire compositions, indicating that the hydrogen bonding exists between the hydroxyl of PVPh and hydroxyl of phenoxy. The negative T g deviation of the PVPh/phenoxy blend indicates the strong intermolecular hydrogen-bonding interaction. The inter-association constant for the PVPh/phenoxy blend is significantly higher than self-association constants of PVPh and phenoxy, revealing that the tendency toward hydrogen bonding between PVPh and phenoxy is more favorable than the intra-hydrogen bonding of the PVPh and phenoxy in the blend.
Relation of glass transition temperature to molecular structure of addition copolymers
Journal of Polymer Science Part C: Polymer …, 1970
An equation is proposed relating the glass transition temperature (TG) of copolymers to their molecular structure in terms of the mole fractions of the various diad sequences of monomer units combined in the copolymer chain, and temperature parameters (Ti$ characteristic of each type of sequence. ij. The equation, an extension of the Gibbs and DiMarzio copolymer TG theory, accounts for the effect on TG of the different types of bonds between repeating units in different diad sequences, and is in its general form: TG = c n ' j i Tif In a binary copolymer of structure [(a) x (b),,] n, corresponding to the sequences -aa-, -ba-, -ub-, and -bb-. The term nIii is the mole fraction of weighted according to the number of rotatable bonds per sequence, aii, and n'ii = nila ij/ (nqaii). The variation in the distribution of sequences with overall composition is obtained from the copolymerization reactivity ratios. The theory, which quantitatively describes the sometimes observed maximum or minimum in TGcomposition plots, gives good agreement with published data for 11 copolymer systems. Application of the theory to give homopolymer TG'S by extrapolation is demonstrated. Inter-relations are found with other published theories of copolymer TG.
Polymer, 2002
A series of poly(hydroxystyrene-co-vinylpyrrolidone-co-isobutylstyryl polyhedral oligosilsesquioxanes) (PHS-PVP-POSS) hybrid polymers with various POSS contents was prepared by free radical copolymerization of acetoxystyrene, vinylpyrrolidone with styrylisobutylpolyhedral oligosilsesquioxanes (POSS), followed by selective removal of the acetyl protective group. The POSS content of a hybrid polymer can be effectively controlled by varying the feed ratios of reactants. The T g of the POSS hybrid increases with the POSS content of PHS-PVP-POSS hybrids. The mechanism of T g enhancement in these PHS-PVP-POSS hybrids was investigated using DSC, FTIR and GPC. The formation of the physically cross-linked POSS in these hybrid polymers trends to restrict polymer chain motion and results in significant T g increase.
Effect of Intermolecular Hydrogen Bonding on Low-Surface-Energy Material of Poly(vinylphenol)
The Journal of Physical Chemistry B
We discovered that poly(vinylphenol) (PVPh) possesses an extremely low surface energy (15.7 mJ/m 2) after a simple thermal treatment procedure, even lower than that of poly(tetrafluoroethylene) (22.0 mJ/m 2) calculated on the basis of the two-liquid geometric method. Infrared analyses indicate that the intermolecular hydrogen bonding of PVPh decreases by converting the hydroxyl group into a free hydroxyl and increasing intramolecular hydrogen bonding after thermal treatment. PVPh results in a lower surface energy because of the decrease of intermolecular hydrogen bonding between hydroxyl groups. In addition, we also compared surface energies of PVPh-coPS (polystyrene) copolymers (random and block) and their corresponding blends. Again, these random copolymers possess a lower fraction of intermolecular hydrogen bonding and surface energy than the corresponding block copolymers or blends after similar thermal treatment. This finding provides a unique and easy method to prepare a low-surface-energy material through a simple thermal treatment procedure without using fluoro polymers or silicones.
Polymer, 2014
In this paper, dielectric and calorimetric studies of the small-molecule glass former allyl acetoacetate monomers as well as its newly synthetized homopolymer and copolymers with different styrene composition were performed in both the liquid and glassy states. The molecular dynamics studies by the broadband dielectric spectroscopy and the stochastic temperature modulated differential scanning calorimetry enabled us to explore relaxation processes of examined materials in the wide frequency range. We found that the copolymers reveal two co-existing glass transitions characterized by the glass transition temperatures, which are very close to those of the corresponding homopolymers. These results suggest that the copolymers exhibited some sequences of acetoacetate units with a microphaseseparated morphology in agreement with the value of reactivity ratio previously determined. We investigated effects of copolymerization compositions on the glass transition temperature, the isobaric fragility index, the dielectric and calorimetric intensity, and the dynamic heterogeneity on the glass transitions of the materials.
Journal of Applied Polymer Science, 2021
A series of linear acrylic copolymers based on Isobornyl acrylate (IBOA) and isobutyl acrylate (IsoBA) were elaborated by radical photopolymerization. In addition, several photochemically crosslinked poly(IBOA-co-IsoBA) were prepared by introducing small amounts of 1,6-hexanedioldiacrylate as crosslinking agent. The evolution of the glass transition temperature was determined experimentally by Differential Scanning Calorimetry as a function of composition for both linear and crosslinked poly(IBOA-co-IsoBA), yielding T g values ranging from (~249K) to (~315K). Theoretical modeling was performed applying Fox, Gordon-Taylor and Couchman-Karasz models by simple calculations using experimental data, leading to only fair agreement between theoretical and experimental values, or by applying fitting procedures involving one or two adjustable parameters. Likewise, the Kwei model, known to take into account hydrogen bonding interactions between monomers, could not describe well the evolution of T g , indicating the existence of other factors influencing T g. Finally, a thermodynamic approach based on entropy considerations allowed to attribute an explanation of the evolution of T g .
Macromolecules, 2005
A series of poly(vinylphenol-co-methyl methacrylate) (PVPh-co-PMMA) block and random copolymers were prepared through anionic and free radical polymerizations, respectively, of 4-tertbutoxystyrene and methyl methacrylate and subsequent selective hydrolysis of the 4-tert-butoxystyrene protective groups. Analysis of infrared spectra suggests that the random copolymer possesses a higher fraction of hydrogen-bonded carbonyl groups and a larger interassociation equilibrium constant relative to those of a block copolymer containing similar vinylphenol content because of the different sequence distribution that may arise from the so-called intramolecular screening effect. In contrast, the glass transition temperature of the block copolymer, which has the lower polydispersity index, is higher than that of the random copolymer at the same composition.