Dynamics of Amorphous and Semicrystalline 1,4-trans-Poly(isoprene) by Dielectric Spectroscopy

Abstract

We have studied the dynamics of amorphous 1,4-trans-poly(isoprene) (trans-PI) with different molecular weights using broadband dielectric spectroscopy over a wide range of temperature ∼T g -70 K to T g + 130 K, and frequencies (10 -1 to 10 6 Hz). Avoiding crystallization by quenching, three dielectric processes (global chain, segmental and local relaxations) were observed in order of decreasing temperature. Both the segmental and local relaxations of the here studied trans-PI, were found to be markedly different compared with the corresponding processes in cis-PI. In contrast, the temperature dependence of the relaxation time related to the global chain mode was found to be independent of the chain configuration. However, its relaxation strength was 1 order of magnitude lower in trans-than in cis configuration indicating a small parallel component of the dipole moment in trans configuration. In addition we also studied the dielectric spectra of trans-PI upon crystallization. The kinetics during crystallization as observed by dielectric spectroscopy results independent of molecular weight. During isothermal crystallization the dielectric spectra can be analyzed by a combination of three processes: the R m -relaxation related with the modified amorphous phase, the so-called R CAP -relaxation induced by crystallization and the β-relaxation, the two later only varying in relaxation strength. At the end of isothermal crystallization a percentage of crystallinity about 30% was estimated.

Structural Dependence of the Molecular Mobility in the Amorphous Fractions of Polylactide

“…In Figure 8, the evolution of cooperativity length and fragility index is reported as a function of the content of the crystalline phase (X c ), MAP (X ma ), and residual phases (i.e., the sum of mesophase and RAF [X ra + meso]). We already evoked that the high fragility values obtained for the Th and TCR materials break down the idea of a simple correlation between the degree of crystallinity and the fragility index.As previously discussed, it has been shown that depending on the polymer repeating unit or depending on the crystallization mode, an increase or decrease of the fragility index with an increase of the crystalline phase can be observed 81,85 . In our case also, no clear trend can be extracted from the fragility index variation with degree of crystallinity ( Figure 8b).…”

Water dynamics in poly(vinyl pyrrolidone)–water solution before and after isothermal crystallization

“…We chose three crystallization temperatures (T c = 215.15, 219.15 and 221.15 K) whereas for each temperature the crystallization times were t c = 30, 60, 150, 180, 360, and 570 min, respectively. Note that this procedure was successfully applied for crystalline polymers and widely discussed in the literature [12][13][14].…”

Preparation of epoxidized Eucommia ulmoides gum and its application in styrene‐butadiene rubber (SBR)/silica composites

“…This gum, also called gutta percha or balata, is a kind of rubber with a molecular structure of trans ‐1,4‐polyisoprene that crystallizes easily, which is the reason why the E. ulmoides gum can usually be used as plastics, shape memory materials and rubber with different crosslinking degree like synthetic trans ‐1,4‐polyisoprene . Actually, trans ‐1,4‐polyisoprene has been widely used in many fields, such as machinery, chemicals, electronics, transportation, etc . Trans ‐1,4‐polyisoprene has excellent mechanical properties, including long fatigue life, good abrasion resistance, and low heat buildup .…”