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Heterophase water-in-oil polymerization of acrylamide by a hybrid inverse-emulsion/inverse-microemulsion process

Heterophase water-in-oil polymerization of acrylamide by a hybrid inverse-emulsion/inverse-microemulsion process. Hernandez-Barajas, Jose; Hunkeler, David (Department of Chemical Engineering, Vanderbilt University, Nashville, TN 37235, USA). Polymer, 38(22), 5623-5641 (English) 1997 Elsevier. CODEN: POLMAG. ISSN: 0032-3861. DOCUMENT TYPE: Journal CA Section: 35 (Chemistry of Synthetic High Polymers) Heterophase water-in-oil polymns. of acrylamide have been conducted in the presence of blends of non-ionic stabilizers at moderate monomer concns. (20%). The initial monomeric system is located outside the inverse-microemulsion domain, yet close to the inverse-macroemulsion/inverse-microemulsion phase boundary. A turbid, viscous and unstable dispersion is produced at the outset and during the intermediate stages of the polymn. This evolves to an inviscid and non-settling system at high conversions. Transparent inverse latices can also be produced provided that the polymns. are conducted semi-adiabatically. Small-angle neutron scattering (SANS) studies of the initial monomer and reacting systems have found the latexes to be particulate with a particle diam. of 150 nm, independent of conversion. The SANS intensities can be fitted using a polydisperse spherical particles model. Therefore, these heterophase water-in-oil polymn. systems seem to follow an inverse-macroemulsion-like mechanism. The hybrid inverse-microemulsion/inverse-macroemulsion polyacrylamides produced herein have a smaller radius of gyration in aq. media relative to those produced by either soln. polymn. or a true inverse-macroemulsion polymn. of the same wt.-av. mol. wt. This is likely due to a large no. of intramol. interactions, such as hydrogen bonds, which are induced by the collapsed nature of the polymer chains in the inverse-microemulsion droplets. The wt.-av. mol. wt., the radius of gyration and the particle diam. of the final latex are relatively independent of the polymns. conditions such as initiator level, hydrophilic-lipophilic balance (HLB), temp. and phys. changes occurring during polymn. From a kinetic point of view, the mol. wts. of these systems are controlled by transfer to monomer, while transfer to interfacial emulsifier is the polymn. rate controlling step. A reaction mechanism consisting of a no. of elementary reactions was proposed for these heterophase-water-in-oil polymns. Agreement with the exptl. data is good at different levels of initiator, HLBs and temp. Despite the limitations of this heterophase water-in-oil polymns. (the moderate emulsifier levels, low radius of gyration and its inability to increase the wt.-av. mol. wt. beyond 106 daltons), this polymn. process can produce final latexes that are transparent and non-settling with small particles (< 150 nm). This allows post-reaction chem. 57171-56-9 are also occured in this study. modification, e.g. by the Mannich reaction. .