ABSTRACT:The heat of fusion of cellulose triacetate was determined from the melting point depression to be 2360cal mol-1 (9.87 kJ mol-1 ). The melting temperatures of thermally reversible gels of cellulose acetate in benzyl alcohol were measured over a range of polymer concentrations. The reciprocal of the gel melting temperature vs. In v2xw plot is linear, where v2 is the polymer volume fraction in the gel and xw is the weight-average degree of polymerization. The plot was analysed according to the thermodynamic theory of the melting of a gel and the crosslinking loci in the gel were inferred to be crystallites consist of triacetyl glucose units.KEY WORDS Cellulose Triacetate I Cellulose Diacetate I Acetyl Cellulose I Heat of Fusion I Gel I Sol-Gel Transition IThe sol-gel transition of secondary cellulose acetate has been receiving attention. The supramolecular structure of cellulose acetate gel is important for understanding the properties of cellulose acetate films prepared by the solvent cast and evaporation method, since the films are technically important for reverse osmosis. The thermally reversible gel formation of cellulose acetate in benzyl alcohol has been studied by several authors. 1 • 2 Recently, Goebel and Berry 3 investigated the supramolecular structure of the gel by light scattering and elasticity measurements. They concluded that the nonrandom character of the cross linking loci in the gel causes the smallangle light scattering. Furthermore, they estimated that the equivalent diameter D of the cross linking loci was 147 A from low-angle X-ray scattering and the formation of the cross linking loci was attributed to the three dimensional nucleation process. However, the length of the crystallite could not be estimated.In preceding papers of this series, one (AT) of the authors developed a thermodynamic theory for the melting of thermally reversible gels, assuming that cross linking locus is the crystallite of length ( units. 4 Despite that the melting point of gel is not the thermodynamic singularity, 4 according to this theory, the melting temperature of the gel (Tmg) is given by (1) In this equation, !1h 0 is the heat of fusion per crystalline monomer unit, Tm 0 is the melting temperature of pure polymer, (Jec is the end interfacial free energy of the crystallite, B' is the cohesive energy density of interaction between the crystalline unit A and the solvent medium which consists of a diluent and noncrystalline units, VA, V 1 are the molar volumes of the crystalline unit and the solvent, respectively, v 2 is the volume fraction of the polymer in the gel, X A is the mole fraction of crystalline unit and xw is the weight-average degree of polymerization. Equation 1 has been applied to evaluate the crystalline length (and interfacial free energy (Jec for many thermally reversible gels and ( thus evaluated compared favorably with (values estimated by other methods such as spectroscopy, elasticity and swelling of gels. 5 • 6 • 7 671
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.