Glass transition and dynamics of phosphate esters dissolved in two glassy polymer matrices

Cauley, B. J.; Cipriani, Ciera E.; Ellis, Keith C.; Roy, Anupam; Jones, Alan A.; Inglefield, Paul T.; Mckinley, B. J.; Kambour, R. P.

doi:10.1021/ma00002a010

Cited by 40 publications

(25 citation statements)

References 11 publications

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“…They mentioned that the reported values in the literature were well above its decomposition temperature. DSC method was not sensitive enough to trace the transitions when there were small changes in heat capacity (Cauley et al, 1991;Quinn et al, 1988). However, the 1 H signal showed high immobility in region 1 (moisture: 0-3 g/100 g dry solids) and even the mobility of the liquid like component was retarded.…”

Section: Water Mobility Conceptmentioning

confidence: 99%

Food stability determination by macro–micro region concept in the state diagram and by defining a critical temperature

Rahman

2010

Journal of Food Engineering

121

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Section: Water Mobility Conceptmentioning

confidence: 99%

Food stability determination by macro–micro region concept in the state diagram and by defining a critical temperature

Rahman

2010

Journal of Food Engineering

121

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“…In contrast to the more widely studied plasticizers, antiplasticizers also depress T g , but these additives increase the stiffness (shear or bulk modulus) of polymeric materials in the glass state. [8][9][10][11] This stiffening is of great importance for preservation of biomaterials, such as foods, tissues, and drugs, and for enhancing the scratch resistance of polymer films, controlling the brittleness and other non-linear mechanical properties of polymer materials, etc. Thus, antiplastization has many practical applications.…”

Section: Introductionmentioning

confidence: 99%

Plasticization and antiplasticization of polymer melts diluted by low molar mass species

Stukalin

Douglas

Freed

2010

The Journal of Chemical Physics

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An analysis of glass formation for polymer melts that are diluted by structured molecular additives is derived by using the generalized entropy theory, which involves a combination of the AdamGibbs model and the direct computation of the configurational entropy based on a lattice model of polymer melts that includes monomer structural effects. Our computations indicate that the plasticization and antiplasticization of polymer melts depend on the molecular properties of the additive. Antiplasticization is accompanied by a "toughening" of the glass mixture relative to the pure polymer, and this effect is found to occur when the diluents are small species with strongly attractive interactions with the polymer matrix. Plasticization leads to a decreased glass transition temperature Tg and a "softening" of the fragile host polymer in the glass state. Plasticization is prompted by small additives with weakly attractive interactions with the polymer matrix. The latter situation can lead to phase separation if the attractive interactions are sufficiently strong. The shifts in Tg of polystyrene diluted by fully flexible short oligomers (up to 20 % mass of diluent) are evaluated from the computations, along with the relative changes in the isothermal compressibility at Tg (a "softening" or "toughing" effect) to characterize the extent to which the additives act as antiplasticizers or plasticizers. The theory predicts that a decreased fragility can accompany both antiplasticization and plasticization of the glass by molecular additives. The general reduction in the Tg and fragility of polymers by these molecular additives is rationalized by analyzing the influence of the diluent's properties (cohesive energy, chain length, and stiffness) on glass formation in diluted polymer melts. The description of glass formation at fixed temperature that is induced upon increasing the diluent concentration directly implies the Angell equation (τα ∼ A exp{B/(φ0, p − φp)}) for the structural relaxation time as function of the polymer concentration, and the computed "zero mobility concentration" φ0, p scales linearly with the inverse polymerization index N .

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“…Dynamics of low molecular weight molecules dissolved in polymer matrices has been studied long by means of dielectric, 1-8 mechanical, 7,8 NMR, 6,7,9,10 light scattering, 7 fluorescence depolarization, 11 ESR, 12 and thermal methods. 6,13 Adachi et al 4 and Yoshizaki et al 1 reported the dielectric behaviors of the systems consisting of polystyrene (PS) and alkylbenzene such as toluene, ethylbenzene and butylbenzene.…”

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Dielectric Study of Dynamical Heterogeneity in Blends of Polystyrene and Low Mass Compounds

Hori

Urakawa

Adachi

2003

Polym J

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ABSTRACT:We investigated the dielectric relaxation in blends of 4-n-pentyl-4 -cyanobiphenyl (5CB) and polystyrene (PS) in order to examine the size effect of low mass molecules on the cooperativity of local dynamics. To obtain the dielectric data in the isotropic state, the phase diagram was produced. The temperature (T ) dependence of the dielectric loss factor ε of PS/5CB blends containing 20 to 30 wt% of 5CB exhibited a bimodal peak near the calorimetric glass transition temperature T g . The bimodal peak was resolved into two peaks termed α and β. The α process locates above T g and can be assigned to cooperative motions of the PS segments and the 5CB molecules. The β process is responsible to independent reorientation of the 5CB molecules in the glassy PS matrix. The α and β loss peaks tend to merge with increasing T . This behavior contrasts to the dielectric behavior of the PS/toluene system which exhibits loss peaks due to segmental motions of PS and rotation of the toluene molecules in well separated temperature regions. The toluene molecule has a size of ca. 1/3 of the 5CB molecule and does not move cooperatively with PS but the 5CB molecule does. From the intensity of the α and β peaks, the fraction of the 5CB molecules moving cooperatively with PS has been estimated to be 0.25 and 0.63 for the blends containing 30 and 20 wt% of 5CB, respectively.KEY WORDS Polystyrene / 4-n-Pentyl-4 -cyanobiphenyl / Dielectric Relaxation / Dynamical Heterogeneity / Cooperativity / Diluent / Segmental Motion / Dynamics of low molecular weight molecules dissolved in polymer matrices has been studied long by means of dielectric, 1-8 mechanical, 7, 8 NMR,6,7,9,10 light scattering, 7 fluorescence depolarization, 11 ESR,12 and thermal methods. 6, 13 Adachi et al. 4 and Yoshizaki et al. 1 reported the dielectric behaviors of the systems consisting of polystyrene (PS) and alkylbenzene such as toluene, ethylbenzene and butylbenzene. It was reported that the relaxation due to rotation of the solvent molecules (β process) and that due to segmental motions of PS (α process) occur separately in different temperature-frequency regions. 1, 4 Similar bimodal mobilities of components are reported for various systems consisting of large and small molecules. 5,6,9,10 This behavior is not in harmony with a generally believed view of cooperativity 14-18 of local motions in supercooled liquids near the glass transition temperature T g . For instance if the PS chains and the toluene molecules in the PS/toluene system move cooperatively, the splitting into the two different relaxation processes would not occur. Such behaviors have been reported even for miscible polymer blends and are called "dynamical heterogeneity". 19,20 However in those literatures referred above, the interest has been centered mostly on the spectral shapes of the relaxation processes and the relationship between the dynamical heterogeneity and the cooperativity has been scarcely investigated.What factors result in the dynamical heterogeneity in polymer/diluent systems? ...

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Glass transition and dynamics of phosphate esters dissolved in two glassy polymer matrices

Cited by 40 publications

References 11 publications

Food stability determination by macro–micro region concept in the state diagram and by defining a critical temperature

Food stability determination by macro–micro region concept in the state diagram and by defining a critical temperature

Plasticization and antiplasticization of polymer melts diluted by low molar mass species

Dielectric Study of Dynamical Heterogeneity in Blends of Polystyrene and Low Mass Compounds

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