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The design of chemiluminescent degradable particles is largely an unexplored field. We, herein, pioneer self-reporting chemiluminescent microspheres, allowing one to readily monitor their degradati...

Conventional pulsed laser polymerization coupled with size exclusion chromatography (PLP-SEC) as well as multipulse pulsed laser polymerization has been employed to study the depropagation kinetics of the sterically demanding 1,1-disubstituted monomers dicyclohexyl itaconate (DCHI), dibutyl itaconate (DBI), and dimethyl itaconate (DMI). The effective rate coefficient of propagation, k(p)(eff) was determined in bulk and solution of cyclohexanone (DCHI) and N-methylformamide (DMI) for monomer concentrations between 1.5 < c(M)(0) < 7.1 mol L-1 in the temperature range 0 < T < 90 degrees C. The resulting Arrhenius plots (i.e., In k(p)(eff) vs 1/RT) displayed a significant curvature in the higher temperature regimes and were analyzed in their respective linear parts to yield the activation parameters of the forward reaction. In the temperature region where no depropagation was observed, the following set of Arrhenius parameters for k(p) were obtained for the bulk systems: DCHI (E-p 26.5 M mol(-1), In A(p)/L mol(-1) s(-1) = 11.5), DBI (E-p = 21.3 kJ mol(-1), In A(p)/L mol(-1) s(-1) = 10.4), DMI (E-p 27.8 kJ mol(-1), In A(p)/L mol(-1) s(-1) = 13.5). In addition, the k(p)(eff) data were analyzed in the depropagation regime for DCHI, resulting in estimates for the associated enthalpy and entropy (Delta H = -53.5 M mol(-1) and AS = -142.3 J mol(-1) K-1) of polymerization. The value for the heat of polymerization was independently measured via on-line differential scanning calorimetry (DSC) as well (Delta H = -55.0 kJ mol(-1)). Delta H of DBI and DMI were also determined via DSC or are available in the literature (Delta H = -42.0 and -60.5 M mol(-1)). These numbers were used to determine the respective entropies of polymerization for both monomers (Delta S = -110 and -156 J mol(-1) K-1) by a fitting procedure of the k(p)(eff) data. DBI polymerization displays significantly different activation parameters as well as thermodynamic properties in comparison with the corresponding DCHI and DMI polymerizations. With decreasing monomer concentration, it is increasingly more difficult to obtain well-structured molecular weight distributions. The DCHI system displayed a significant reduction in k(p)(eff) with increasing cyclohexanone concentration.

Styrene was polymerized under a source of ultraviolet radiation in the presence of certain thiocarbonylthio compounds. Use of 1-phenylethyl phenyldithioacetate (1-PEPDTA) produced well-defined polymers with molecular weights close to those predicted from theory, up to conversions of 30%. The mechanism of polymerization was examined and shown to proceed via reversible addition-fragmentation chain transfer, as opposed to reversible termination with a thiocarbonylthiyl radical. UV-induced decomposition of the dithioester moiety in 1-PEPDTA and 1-phenylethyl dithiobenzoate (1-PEDB) mediated RAFT polymerizations was followed using UV/vis spectrophotometry, 1-PEPDTA decomposed much slower than 1-PEDB. Analysis of the decomposition products of 1-PEPDTA with gas chromatography/mass spectrometry was used to elucidate a possible mechanism for its degradation, suggesting that both 1-phenylethyl and benzyl radicals are decomposition products.

Very recently, Millard et al. have reported the polymerization of acrylic acid and N-isoproylacrylamide under γ-irradiation via RAFT in aqueous media. However, there are certain practical limitations of employing γ-irradiation for commercial applications compared to ultraviolet (UV) radiation...