Polymers solvent activities

Tseng et al. [164] suecessfully used UNIFAC to optimize polymer-solvent interactions in three-solvent systems, determining polymer activity as a function of the solvent eomposition. The composition yielding the minimum in polymer aetivity was taken as the eriterion for optimum interaetion, and it eompared well with experimental measurements of dissolution rate and solution clarity. Better agreement was obtained using UNIFAC than using solubility parameter methods. 

C. Case III Prediction of Solvent Activity in Polymer Systems ... 

It is an arduous task to develop thermodynamic models or empirical equations that accurately predict solvent activities in polymer solutions. Even so, since Flory developed the well-known equation of state for polymer solutions, much work has been conducted in this area [50-52]. Consequently, extensive experimental data have been published in the literature by various researchers on different binary polymer-solvent sys-... 

The purpose of this case study was to develop a simple neural network based model with the ability to predict the solvent activity in different polymer systems. The solvent activities were predicted by an ANN as a function of the binary type and the polymer volume frac-... 

Predicting Polymer Activities in Polymer Solvent Binaries... 

From the weak dependence of ef on the surrounding medium viscosity, it was proposed that the activation energy for bond scission proceeds from the intramolecular friction between polymer segments rather than from the polymer-solvent interactions. Instead of the bulk viscosity, the rate of chain scission is now related to the internal viscosity of the molecular coil which is strain rate dependent and could reach a much higher value than r s during a fast transient deformation (Eqs. 17 and 18). This representation is similar to the large loops internal viscosity model proposed by de Gennes [38]. It fails, however, to predict the independence of the scission yield on solvent quality (if this proves to be correct). 

A combination of anionic and ATRP was employed for the synthesis of (PEO-b-PS) , n = 3, 4 star-block copolymers [148]. 2-Hydroxymethyl-l,3-propanediol was used as the initiator for the synthesis of the 3-arm PEO star. The hydroxyl functions were activated by diphenylmethyl potassium, DPMK in DMSO as the solvent. Only 20% of the stoichiometric quantity of DPMK was used to prevent a very fast polymerization of EO. Employing pentaerythritol as the multifunctional initiator a 4-arm PEO star was obtained. Well-defined products were provided in both cases. The hydroxyl end groups of the star polymers were activated with D PM K and reacted with an excess of 2-bromopropionylbro-mide at room temperature. Using these 2-bromopropionate-ended PEO stars in the presence of CuBr/bpy the ATRP of styrene was conducted in bulk at 100 °C, leading to the synthesis of the star-block copolymers with relatively narrow molecular weight distributions (Scheme 72). 

Of the preponderance of small ions, the colligative properties of polyelectrolytes in ionising solvents measure counterion activities rather than Molecular weight. In the presence of added salt, however, correct Molecular weights of polyelectrolytes can be measured by membrane osmometry, since the small ions can move across the membrane. The second virial coefficient differs from that previously defined, since it is determined by both ionic and non-ionic polymer-solvent interactions. 

Among direct production costs, we can list raw materials, utilities, direct operation labour, maintenance, catalysts, royalties, etc. In our case, solvents (THF and pressurised CO2), polymer, and active ingredient are needed on a daily basis. The corresponding quantities were determined using the process simulator, as described in paragraph 8.3.3. In this discussion, additional solvent (THF) losses are supposed to equal 5% of the total flow rate entering the... 

Elbro, H.S., Fredenslund, A., Rasmussen, P. A new simple equation for the prediction of solvent activities in polymer solutions Macromolecules 1990,23 (21) 4707. 

High, M.S., Danner. R.P. Prediction of solvent activities in polymer solutions. Fluid Phase Equilibria, 1990,55 1-15. 

Oishi. T.. Prausnitz, J.M. Estimation of solvent activities in polymer solutions using a group-contribution method. Ind. Eng. Chem. Process Res. Dev., 1978, 17(3) 333-339. 

Copolymer active groups (mol.%) Polymer Solvent sitiona M Ref. 

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