Naslov
Thermodynamic Properties of Cellulose Diacetate in Mixed Solvents

Autori
Rogošić, Marko ; Pintarić, Božena ; Mencer, Helena Jasna

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
7th European Polymer Federation Symposium on Polymeric Materials: Polymers Friendly for the Environment : Book of Summaries / - Szczecin : Wydawnictwo Uczelniane Politechniki Szczecińskiej, 1998, 263-263

Skup
European Polymer Federation Symposium on Polymeric Materials: Polymers Friendly for the Environment (7 ; 1998)

Mjesto i datum
Szczecin, Poljska, 20.09.1998. - 24.09.1998

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
cellulose diacetate; preferential adsorption; mixed solvents

Sažetak
Cellulose diacetate (CDA) is an environment-friendly, water-compatible polymer that is commonly produced by the acetylation of a purely natural polymer - cellulose. CDA is widely adopted for the preparation of various types of films, coatings and membranes for different purposes. CDA meets quite restrictive requirements of many specific applications, such as drinking water production, food packaging, etc. In most cases, CDA-products are prepared from the solution, and the best properties are generally obtained when mixed solvents are used. The thermodynamic behavior of diluted solutions of CDA in mixed solvents has not been thoroughly investigated so far. Rather complex investigations in mid-concentration regime were more common, but they were subjected to the substantial amount of empiricism. In this contribution the diluted solution properties of CDA in single solvents (formic acid (FA), acetone(A), N, N-dimethyl formamide (DMF)) and in mixed solvents (acetone with FA, DMF, N-methyl formamide (NMF) and formamide (F), respectively) were investigated by the low-angle laser light scattering method, as well as by the diluted solution viscometry method. The main experimental results comprised second virial coefficient values, A2, preferential adsorption coefficient values, a, and limiting viscosity number values, [h]H. The results were interpreted in terms of specific interactions among solution components. The thermodynamic properties of CDA molecules in the investigated mixed solvents depend on the subtle balance of various types of specific interactions, mainly H-bonds. The same balance of interactions influences the dimensions of CDA molecules in solution as well. Inherent rigidity of CDA in a solid state is a consequence of intermolecular H-bonding. Upon dissolution, a portion of those H-bonds is broken and new H-bonds are formed between CDA and solvent molecules. Consequently a strong solvation is achieved. Basic solvents (acetone and DMF) primarily solvate hydroxyl groups of CDA and both the intensity and the direction of preferential solvation are determined by the preferred heteroassociation of solvent molecules (dipole interactions). Acidic solvents (formic acid, formamide, NMF) primarily solvate acetyl groups of CDA. In this case the preferential solvation behaviour is determined by the autoassociation properties of acidic solvents (H-bonding). The autoassociaton of acidic solvent molecules is responsible for the intramolecular and intermolecular bridging of CDA-molecules as well. This phenomenon gives rise to the structuring of more concentrated CDA-solutions, which is of key importance when technical CDA-membranes are to be prepared. Structure of CDA-solutions may be varied by changing the composition of a mixed solvent, composed of one basic solvent (usually acetone) and one acidic solvent prone to autoassociation. Within the framework of this work it is proved that preliminary studies of the structuring of CDA-solutions may be performed even in diluted solution regime. On the basis of preliminary studies a suitable range of solvent compositions may be chosen and necessary but rather complex investigations in mid-concentration regime may then be performed only in that, quite restricted composition range.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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