Rheological and Thermal Properties of Narrow Distribution Poly(ethyl acrylate)s

Abstract

In the present work, we characterize the rheological behavior of 10 nearly monodisperse poly-(ethyl acrylate) samples, whose molar mass ranges from 1200 to 150 000 g/mol. The poly(ethyl acrylate)s were obtained by means of a controlled/living radical polymerization technique. The time-temperature superposition principle works, and the T dependence of the horizontal shift factor a Tr (T) is fairly well described by the Williams-Landel-Ferry law. Furthermore, the zero-shear viscosity dependence on the temperature, for all the investigated samples, has resulted to be well described by means of Vogel-Fulcher laws. The mass dependence of thermal parameters such as the Vogel temperature T 0 and the pseudo-activation energy T b has been worked out and compared to the mass dependence of the glass transition temperature T g . This leads us to propose here a coherent way to describe their behavior and estimate several microscopic parameters in terms of free volume. Moreover, the molar mass dependence of material parameters has been investigated. The zero-shear viscosity η at different temperatures has been evaluated, and the critical mass value has been found to be M c ) 26 000 g/mol. The ratio between the critical M c and the entanglement mass M e has been found to be about 2.2 from the evaluation of the plateau modulus G N 0 . A mass dependence analysis of the steady-state compliance J e 0 has also been carried out from which the second critical mass M c ′ is inferred.

The effects of strain rate and temperature on commercial acrylic artist paints aged one year to decades

“…Values of M w are also given where available. Andreozzi et al [40] have published VF parameters for p(EA), showing an increase of B and T ∞ with increasing M w . Their results also indicate a decrease of E g and m with M w for the materials.…”

Dynamics, fragility, and glass transition of low-molecular-weight linear homopolymers

“…These samples belong to a series of PEA linear homopolymers synthesised following an atom transfer radical polymerization [5] using ethyl 2-bromo propionate as initiator, which becomes indistinguishable from ethyl acrylate repeat unit once inserted in the macromolecule. The averages M n and M w , and polydispersity M w /M n were determined by size exclusion chromatography using monodisperse polystyrene for the calibration [5] (Table 1). Differential calorimetry measurements were carried out by means of a DSC7 Perkin-Elmer calorimeter in order to obtain the glass transition temperatures T g (Table 1).…”

“…In this work, the molar mass dependence of the glass transition temperature T g , fragility indexes, and of the dynamic modulus master curve of nearly monodisperse unentangled poly(ethyl acrylate) (PEA) melts are studied and discussed. All the results are interpreted in a coherent framework based on the free-volume concept [5]. This approach also allows one to predict the thermal response, and in particular the friction coefficient, at a given mass value, after having characterised homologue samples in a proper mass range.…”

“…In a previous paper [5], we showed how, in a revised free-volume framework, it is possible to interpret the mass dependence of WLF/VF parameters, and how to extend the Fox-Flory law to fit better T g values for the oligomers. In this paper, we show how this model can also be applied to the fragility indexes and extended to other melts such as poly(methyl methacrylate) (PMMA) polymers.…”

“…Besides T , the only mass-dependent quantity in the expression of τ R is the monomeric friction coefficient ζ 0 , whose temperature dependence is expected to be the same as viscosity [2,5]. The total complex shear modulus G * is given by the contribution of the overall monodisperse components G * mono (ω, M ) of the molar mass distribution w(M ) = dW (M )/ dlog M , where W (M ) is the weight fraction of chains with molar mass lower than M :…”