Structural/compositional nanoheterogeneity and glass‐transition plurality in amorphous polycyanurate–poly(tetramethylene glycol) hybrid networks

Abstract

The nanostructure and dynamics over the temperature range of −140 to 300 °C were studied in a series of polycyanurate (PCN)–poly(tetramethylene glycol) (PTMG) hybrid networks by wide‐angle X‐ray diffraction and small‐angle X‐ray scattering, with a synchrotron radiation setup, and by differential scanning calorimetry (DSC) and laser‐interferometric creep rate spectroscopy (CRS) techniques, respectively. The networks were synthesized from the dicyanate ester of bisphenol A and hydroxyl‐terminated PTMG with a number‐average molecular weight of 1.000 g/mol; the PTMG content varied from 0 to 40 wt %, and the degree of its chemical incorporation into the PCN network changed from 78.8 to 97%. The noncrystalline structure and considerable structural nanoheterogeneity of the hybrid networks were shown. CRS/DSC analysis revealed a complicated dynamic behavior, that is, a wide dispersion of glass transitions in the hybrid networks due to the presence of nanodomains with different degrees of rigid crosslinking (i.e., compositional nanoheterogeneity). Besides the physical significance, the plurality of glass transitions found in the PCN–PTMG hybrid networks was also of practical interest because it resulted in increasing mechanical strength of the brittle PCN network due to microplasticity arising at room temperature and moderate temperatures and the retention of some rigidity and creep resistance at temperatures much higher than the basic glass‐transition temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3261–3272, 2005

Effect of ionic liquids on kinetic parameters of dicyanate ester polycyclotrimerization and on thermal and viscoelastic properties of resulting cyanate ester resins

“…The spectrum of CER/[OMIm][BF 4 ] showed only characteristic absorbance bands of both individual components (see Figure 4, curve (3) was proposed for the formation of cyanurate cycles from DCBE polymerization being catalyzed by [HEAIm][Cl] ( Figure 6). Our hypothesis was based on the well-known mechanisms of polycyclotrimerization of CERs in the presence of hydroxy [1,[32][33][34][35] and amino [36,37] compounds. First, during the mixing procedure, the -OCN groups of DCBE could react with hydroxyl groups of [HEAIm][Cl] with formation of imidocarbonate O-C(=NH)-O fragment ( Figure 6, compound 2), which further reacted with a second DCBE molecule with formation of a stabilized dimer ( Figure 6, compound 3) Figure 6, compound 6) with release of ROH (monocyanate of bisphenol E).…”

“…Obviously enough, Figure 10 shows the temperature dependence of storage modulus (E′) and loss factor (tan δ) for neat CER and CER/IL networks. All the samples were characterized by high α relaxation temperature values (T α > 240°C, Table 4), as typically found for thermostable cross-linked polymers, due to high temperature resistance of cross-links and high cross-linking density of polymer networks [1][2][3][4][5][6][32][33][34][35]. Unpredictably, a significant effect of the low IL content (i.e., 1.0 wt%) on the viscoelastic properties of all CER/IL networks was found compared to those of pure CER ( Figure 10, Table 4).…”

Relaxation phenomena in latex polymer materials modified by ionic phthalocyanine

“…Taking into consideration the data of [25][26][27][28][29][30], the disappearance of this peak of dissipative losses can be related to inter action of its carboxyl groups with ionic phthalocya nine, on the one hand, and a decrease in the density of the "shell" polymer block, on the other. The overall result is relaxation uniformity of the modified polymer manifested in its single peak spectrum of dissipative losses.…”

Relaxation inhomogeneity of the structure of latex polymers modified with water-soluble phthalocyanine

“…According to the concepts developed in [14][15][16][17][18][19], we likewise associated the change in the relaxation spectrum with the disturbance of intermo lecular interactions in the modified polymer due to the contact between the carboxyl containing polymer core and ionic phthalocyanine, on the one hand, and the decrease in the packing density of the polymer block in the shells of the latex particles in the presence of a modifier, on the other hand [13]. In addition, it has been found that, at temperatures above the glass transition temperature, a much higher temperature is required to unfreeze the mobility of polymer segments shielded by bulky phthalocyanine molecules [13].…”