Dependence of viscoelastic spectrum width on the structure of model imperfect networks prepared by endlinking

Abstract

Using the theory of branching processes, structural parameters such as the molecular weights of elastically active network chains (EANCs), including dangling chains, backbone EANCs and dangling chains of networks built up by the alternating polyaddition of a bi-and trifunctional monomer, are characterized. The theory is compared with viscoelastic data on polyurethane networks prepared from poly(oxypropylene)triols and diisocyanate at various initial ratios of functional groups; in the calculation, the distribution of functionalities of the triols used and the possible incompleteness of the reaction is taken into account. The comparison reveals that both the length of the backbone EANC and the length of dangling chains contribute to the total width of the retardation spectrum.

Epoxy networks and hydrogels prepared from α,ω-diamino terminated poly(oxypropylene)-b-poly(oxyethylene)-b-poly(oxypropylene) and polyoxypropylene bis(glycidyl ether)

“…The r-dependence of the mass fraction of sol, w s , listed in Table 1 is in agreement with the trend predicted by the theory of branching processes [28,32]. An elevated value of w s found for the stoichiometric network (w s = 0.125, see Table 1) testifies a certain imperfectness of the curing process that can originate from the presence of a small amount of non-functionalized chains in ED-2003, uncompleted curing reaction or cyclization [38,39].…”

“…Simple epoxy networks have been used as model networks for testing of network formation and rubber elasticity theories [28,[30][31][32]. In a detailed review of curing of epoxy networks [28], Dušek concludes that ''.…”

Chemical Clusters in Polyurethane Networks. SAXS, Photoelastic and Dynamic Mechanical Behavior of Networks from Poly(Oxypropylene)Diol, Diisocyanate, and Trimethylolpropane Prepared One‐Stage and Two‐Stage Process

“…The viscoelastic behavior (shape of mechanical function on frequency and temperature) was affected not only by the cross-linking density but also by the detailed structure of elastically active network chains. [6,9,10] With increasing deviation from stoichiometry, an increase in damping at lowest frequencies was observed.…”

“…It was discussed earlier [3,11,12] that a structure with more extended clusters is expected in networks prepared in a one-stage process in comparison with the networks prepared in a two-stage process. If in these three-component systems network formation takes place with an excess of OH groups up to the full conversion of minority (NCO) groups, the network contains variously clustered sol and gel, and the structure of elastically active chain (EANC) in the gel is complex [6,10] [many dangling chains (DC) of different cluster sizes are a part of the clustered backbone chain (BC), Fig. 1b].…”

Synthesis and Mesomorphic Properties of New Chiral Liquid-Crystalline Diols

“…Refs. [1][2][3][4]. Introduction of the rigid mesogenic groups into the polymer chain (in the backbone or side chain) usually leads to liquid-crystalline polymers (LCP), which show an intermediate state of aggregation between the crystalline and amorphous structures.…”