Analogue calorimetry for blends of poly(vinyl ester)s and polyacrylates has been studied. Hydrogenated monomers were used as analogues of the corresponding polymers. It is found that isomeric esters differing only in the orientation of the COO group mix with only small heat change, which can be positive or negative. The values of the interaction energy density, B 12 (in cal/cm3), are −0.045, 0.031, and −0.076, respectively, for the following binary mixtures; ethyl acetate + methyl propionate, n-propyl propionate + ethyl butyrate, and phenyl propionate + ethyl benzoate. The negative heat of mixing for the two pairs of very similar liquids, although unexpected, explains why the corresponding polymers are miscible. The small positive heat of mixing for the other pair is sufficient to predict demixing of the corresponding polymers, viz., poly(n-propyl acrylate) and poly(vinyl butyrate), which contradicts the observation of their homogeneous mixing. This suggests that hydrogenated monomers are not always the proper analogues for vinyl polymers for the prediction of the interaction energy. A novel flow calorimeter is also described. H E and V E data for binary mixtures of the above esters are presented.

No abstract

No abstract

A miscible homopolymer–copolymer pair viz., poly(ethyl methacrylate) (PEMA)–poly(styrene‐co‐butyl acrylate) (SBA) is reported. The miscibility has been studied using differential scanning calorimetry. While 1 : 1 (w/w) blends with SBA containing 23 and 34 wt % styrene (ST) become miscible only above 225 and 185 °C respectively indicating existence of UCST, those with SBA containing 63 wt % ST is miscible at the lowest mixing temperature (i.e., Tg's) but become immiscible when heated at ca 250 °C indicating the existence of LCST. Miscibility for blends with SBA of still higher ST content could not be determined by this method because of the closeness of the Tg's of the components. The miscibility window at 230 °C refers to the two copolymer compositions of which one with the lower ST content is near the UCST, while the other with the higher ST content is near the LCST. Using these compositions and the mean field theory binary interaction parameters between the monomer residues have been calculated. The values are χST‐BA = 0.087 and χEMA‐BA = 0.013 at 230 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 369–375, 2000

Dispersion polymerization of acrylamide has been successfully carried out in aqueous tert-butyl alcohol (TBA) media (TBA = 50 − 80 vol %) using poly(vinyl methyl ether) (PVME) as the polymeric stabilizer and ammonium persulfate as the initiator. Polydisperse spherical as well as oval particles are formed. The simultaneous presence of both spherical and oval particles suggests the coalescence of similar size particles (homocoalescence) takes place, leading to polydispersity. The increase of stabilizer concentration leads to a decrease in particle size and an increase in molecular weight. An increase of initiator concentration results in an increase in particle size and a decrease in molecular weight. These observations are in conformity with other dispersion polymerizations reported in the literature. Particle size decreases as the TBA concentration increases, i.e. as the medium polarity decreases. TBA−water mixtures exhibit cosolvency toward PVME, the solvency becoming highest at about 70 vol % TBA. This solvency aspect cannot account for the monotonous decrease of particle size with an increase in TBA concentration. A plot of particle diameter (D̄ n) vs the initial solubility parameter (δ) of the medium gives a straight line unlike the linear relationship between D̄ n and 1/δ reported for dispersion polymerization of nonpolar monomers in polar solvents. This difference in behavior for the two systems can be reconciled if the grafted polymer acts as the true stabilizer.