Statistical Polymerizations Homopolymerizations and Multipolymerizations

Homopolymerizations via FRRPP process normally starts from solution, i.e., the monomer is in a soluble environment. When free radicals are formed from initiator compounds at a high enough temperature, propagation reactions occur and polymer chains are formed. As the polymer radicals attain a high enough chain length, it enters the LCST-based phase envelope and phase separates to form a polymer-rich material. This is where the reaction mechanism of the FREtPP process deviates from conventional solution or dispersion polymerization processes. 

The FRRPP can also be implemented in suspension and emulsion polymerization processes. Its analysis in suspension system has turned out to be straightforward, because the suspension size scale (mm sizes) does not interfere with the reaction mechanism, even if one includes mass and thermal transport effects. In emulsion polymerization systems, the submicron size scale of emulsion particles interfere with thermal and probably mass transport effects in the system. Also, the hydrophobic portions of surfactant molecules could affect the phase equilibrium aspects of the FRRPP system. 

In random copolymerizations, and certainly multipolymerizations, the FRRPP process can result in products that do not seem to contain random segmental monomer distributions. When polymerizing chains are not prematurely terminated in the FRRPP process, the product distribution can adhere to the predictions of monomer reactivity and monomer concentration ratios. With the incorporation of 

Caneba, in Free-Radical Retrograde-Precipitation Polymerization (FRRPP), 

According to the literature (Brandrup et al., 1999), reactivity ratios for AA (1)/VA (2) copolymerization are r = 2.0 and r2 = 0.1. This means that from a reactivity standpoint, AA-radical ends will want to react with AA monomer, while VA-radical ends will also want to react with AA monomer. Thus, if there exists a 50/50 mole ratio of AA to VA in the reactor fluid, AA will tend to add into a growing copolymer chain at 20 times faster than VA the reactivity of AA monomer would normally result in AA-rich and AA-poor chains, due to chain termination. This implies a very active AA monomer, which is the reason why it was well known that VA/AA copolymers with AA contents greater than 10 wt% cannot be produced efficiently. If the introduction of AA in the reactor is controlled, then the reaction of VA will allow the overall control of the propagation rate while keeping polymer radicals live. This will result in the possibility of producing relatively high AA-content copolymers, as opposed to mixtures of AA- and VA-rich polymers with 

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