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Quantum chemical techniques reasonable in practical simulation of carbon-centered radical reactions were evaluated scaling up from addition and cyclization of small radicals to growing chains in homo- , cross- and cyclo- polymerization. The methods preselected via “cost – deviation from experiment” criteria were explored relative to growing molecular systems of radical cyclocopolymerization between divinyl ether and maleic anhydride: alternating cross-propagation with cyclization and side homopolymerization reactions. The following methods were found to be optimal for estimation of activation barriers and thermodynamics parameters: DFT M06-2X with 6-311+G(d) and 6-311+G (2df,p) basis sets or ONIOM M06-2X/6-311+G(d):B3LYP/6-31G(d) – for more complex systems. Spin-restricted open shell calculations by ROMP2/6-311+G (3df, 2p) have shown unfeasible increase in computational costs retaining similar accuracy. The optimal techniques facilitated new mechanistic insights into regulating the polymerization including kinetic-thermodynamic control factors for regulation of furan-/pyran-related isomerism within the chain that is essential for tailoring functionality of the derivatives. The approach builds methodology basis for research of similar macromolecular systems including alike polymeric platforms for preparations of broad biomedical applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Factors of phase separations in solutions of the polyelectrolytes were elucidated. [•] The separations were strictly controlled by pH, ionic strength, and chains length. [•] The transitions occurred rapidly, reversibly, and at enzyme-friendly conditions. [•] The transformations obeyed main regularities inherent in polyelectrolyte complexes. [•] The findings could be of practical use, specifically for antitumor drugs delivery. [ABSTRACT FROM AUTHOR]

Abstract: Copolymer of divinyl ether and maleic anhydride (DIVEMA) is known to possess some anti-tumor and immune-stimulating activity and use as a drug carrier in anti-tumor drug delivery systems. Samples of DIVEMA of different degrees of polymerization were synthesized and characterized. Interaction of the hydrolyzed water-soluble DIVEMA polyanions with poly(N-ethyl-4-vinylpyridinium) cations (PEVP) has been studied. According to the potentiometry data, almost all carboxylic groups of the polyanions were able to form ion pairs with PEVP. In aqueous and water–salt solutions, formation of either soluble or insoluble polyelectrolyte complexes occurred depending on pH, ratio of the oppositely charged groups, and degree of polymerization of PEVP and/or DIVEMA. The phase separations followed general rules revealed by studying mixtures of PEVP and polycarboxylic acids. However in the case of DIVEMA, a significant broadening of the region for insoluble complexes at the expense of the region of soluble complexes was established. The data obtained demonstrate plausible advantages of the complex formation as the non-covalent modification of the polymeric carrier that endow DIVEMA with the ability for reversible soluble–insoluble transformation, in particular at physiological pH and ionic strength. [Copyright &y& Elsevier]