Emulsion Polymerizations at Low Temperatures

Poly(isobutylene) Nanoparticles via Cationic Polymerization in Nonaqueous Emulsions

“… i) Initiated by H 2 O/1,2‐dimethoxybenzene (DMB), [IB]:[AlCl 3 ]:[DMB]:[H 2 O] = 1500:10:9:3, solvent:DCM/ n ‐hexane (33/67 vol%);…”

“…A third system employing a “non‐controlled” cationic polymerization was applied, which is known to produce high‐molecular‐weight PIB (hmPIB) with > 10 5 g mol −1 . Using H 2 O/1,2‐dimethoxybenzene/AlCl 3 as the initiator system, hmPIB was first isolated under homogeneous conditions (entry 11, = 162 000 g mol −1 , PDI = 3.7). In this instance, 67 vol% instead of 40 vol% n ‐hexane was necessary to prevent precipitation of the polymer.…”

“…From the results in entries 1-8, it was found that the DCM/hexane-in-perfl uoroalkane emulsion only produces PIB molecular weights below 30 000 g mol −1 , despite changes in the temperature and initiator systems. Furthermore, the molecular weight values are in agreement with the only other reported use of nonaqueous, fl uorous emulsion polymerization of IB by Bachman et al [ 16 ] Given the similarities between the molecular weights produced in the three different emulsion systems, the initial assumption of unfavorable side reactions seemed unlikely to be the sole determining factor on the produced molecular weight. Rather, we attribute this phenomenon to the partial solubility of alkanes ( δ n -hexane = 7.3 and δ n -pentane = 7.0) in perfl uoroalkanes ( δ PFH = 5.6 and δ n -perfl uoropentane = 5.5), leading to a shift in the "real" composition of the DCM/alkane mixture in the emulsion droplet.…”

“…Furthermore, this change in the solution concentration also explained the higher PDIs achieved during the emulsion polymerization experiments, in comparison to the homogeneous polymerization (entry 8). As , CumCl = cumyl chloride; c) Heating curve at 10 K min −1 ; d) Particles were not stable and did not hold spherical shape; e) Poly(Sb -PFS OR ) emulsifi er [ 14 ] ; f) Bimodal MWD; g) Standard deviation > average particle diameter; h) 2-Chloro-2,4,4-trimethylpentane (CTMP) initiator, n -perfl uoropentane continuous phase, and n -pentane/DCM dispersed phase, -115 °C; i) Initiated by H 2 O/1,2-dimethoxybenzene [ 16 ] polarity of the reaction medium is known to have a profound effect on the IB polymerization by changing the electrostatic interaction between carbocation and TiCl 5 − or Ti 2 Cl 9 − counter ions, a lower ratio between propagation and termination rates was anticipated for the IB emulsion polymerization. [ 30 ]…”

“…Perfluoroalkanes have the benefit of extremely low melting points and therefore, can be successfully utilized as the continuous phase without the need of additives. Indeed, Bachman et al suggested the use of fluorous emulsion systems for PIB preparation in 1949 for the same reason. However, the authors were unable to find a suitable emulsifier and instead applied strong mechanical stirring, otherwise “coagulation proceeded instantaneously, interfered with the stirring and the polymer was of low molecular weight and poor physical properties.”…”