Specific Refractive Index Increments of Polyurethane/Polydimethylsiloxane Segmented Copolymers

Abstract

New polydimethylsiloxane-containing segmented block copolyurethanes were obtained from aromatic or aliphatic diisocyanates, 1,4-butanediol and poly(ethylene glycol)adipate using a multistep polyaddition process. Specific refractive index increments of these segmented copolymers in N,N-dimethyl-formamide have been determined by the Lorenz-Lorentz equation and the corresponding group contributions to the molar refraction and to the molar volume. The results are in good agreement with the experimental values. Also, from the dependence between the specific refractive index increments and the weight fraction of 4,4Ј-methylene diphenylene diisocyanate units, w d , the 0 and d/dw d coefficients have been evaluated and the results are situated between the values reported in literature.

Influence of Hard Segments to Specific Refractive Index Increments of Segmented Poly(Ester Urethane)s

“…These dependencies become complicated for copolymers containing three or more components that largely differ in refractivity. Also, our previous data [10] for poly(ester siloxane)urethanes shows that the experimental values of specific refractive index increments slightly differ from those calculated through the Lorenz-Lorentz equation. [1] Schulz et al [2] found good correspondence of the experimental values with those calculated from group contributions to the molar refraction, using the method proposed by Goedhart [3] and van Krevelen.…”

Viscometric Study of Segmented Poly(ester-urethane) Solutions in Dilute and Extremely Dilute Concentration Domains

“…Thus, the studied poly(ester urethane)s are block copolymers, consisting of two phases designated as soft segments, which are flexible blocks, and hard segments, which are rigid blocks [11]. Hard blocks are also associated with hydrogen bonding and physical crosslinks.…”

“…The polyurethane-solvent interaction parameter can be analyzed by a simplistic, so-called two-parameters theory, where the effective interaction parameter is supposed to be the sum of two interaction parameters, coming from solvent-soft segment and solvent-hard segment interactions, or by the complicated multiple-parameters models that take into consideration more interaction parameters [11,24]. In the present work the studied polyurethanes are multicomponent compounds and the determination of the interactions that may occur is very complicated.…”

“…The absolute molecular weight measurements of segmented polyurethanes by different methods are complicated by the fact that, in addition to the molecular weight distribution, copolymers usually exhibit a distribution of composition [11][12]. The use of multiple monomers instead of two for the polymerization, the possible side reactions yielding to allophanate crosslinking for example, and the generally poor solubility in common solvents are additional complication factors.…”

“…The authors' previous publications [11][12][13][14] present the syntheses and some properties of a series of new segmented and crosslinked polyurethane elastomers. The influence of the polymer structure on thermal stability, the behavior in different organic solvents, and the structure and morphology of these compounds were analyzed.…”