Production of poly(methyl methacrylate) particles by dispersion polymerization with mercaptopropyl terminated poly(dimethylsiloxane) stabilizer in supercritical carbon dioxide

Poly(methyl methacrylate) (PMMA) particles were produced by dispersion polymerization of methyl methacrylate in the presence of mercaptopropyl terminated poly(dimethylsiloxane) (MP-PDMS) in supercritical carbon dioxide at about 30 MPa for 24 h at 65 °C. The particle diameter could be controlled in a size range of submicron to micron by varying MP-PDMS concentration. The MP-PDMS worked as not only a chain transfer agent but also a colloidal stabilizer, which was named tran stab.Part CCLI of the series Studies on suspension and emulsion     

Polymerization of allyl esters of unsaturated acids. VII. Copolymerization of methyl allyl maleate and fumarate with styrene

Radical copolymerizations of methyl allyl maleate (MAM) and methyl allyl fumarate (MAF) with styrene (St) are carried out in bulk using AIBN as an initiator at 60°C, and their copolymerization behaviors are compared in detail. The different rate features are observed with each other; thus in the MAF-St copolymerization the rate was quite enhanced and, also, the maximum rate was found at the molar ratio of 1:1 in the monomer feed, whereas no maximum phenomenon of the rate was apparent for the MAM—St copolymerization. The copolymerizability of MAF with St was quite high, whereas that of MAM was very poor. The cyclization of MAM or MAF was hindered by the highly reactive St monomer. These results are discussed in terms of the formation of the charge—transfer complex between MAF and St and, furthermore, the cyclocopolymerization kinetics involving the 17 elementary reactions as the propagation reactions.     

Muonium formation and the “missing fraction” in vapors

The vapor phase fractional polarizations of positive muons thermalizing as the muonium atom (P _M) and in diamagnetic environments (P _D) has been measured in H₂O, CH₃OH, C₆H₁₄, C₆H₁₂, CCl₄, CHCl₃, CH₂Cl₂ and TMS, in order to compare with the corresponding fractions measured in the condensed phases. There is a marked contrast in every case, with the vapor phase results being largely understandable in terms of a charge exchange/hot atom model. Unlike the situation in the corresponding liquids, there is no permanent lost fraction in the vapor phase in the limit of even moderately high pressures (1 atm); at lower pressures, depolarization is due to hyperfine mixing and is believed to be well understood. For vapor phase CH₃OH, C₆H₁₄, C₆H₁₂, and TMS therelative fractions are found to be pressure dependent, suggesting the importance of termolecular hot atom (or ion) reactions in the slowing down process. For vapor phase H₂O and the chloromethanes, the relative fractions are pressure independent. For CCl₄,P _M=P _D0.5 in the vapor phase vs.P _D=1.0 in the liquid phase; fast thermal reactions of Mu likely contribute significantly to this difference in the liquid phase. For H₂O,P _M 0.9 andP _D0.1 in the vapor phase vs.P _D 0.6 andP _M0.2 in the liquid phase. Water appears to be the one unequivocal case where the basic charge exchange/hot atom model is inappropriate in the condensed phase, suggesting, therefore, that radiation induced spur effects play a major role.     

Polymerization of allyl esters of unsaturated acids. V. Cyclopolymerization of methyl allyl fumarate

The kinetics of radical polymerization of methyl allyl fumarate (MAF) is discussed in terms of cyclopolymerization and compared with the polymerization results of methyl allyl maleate (MAM) as a cis isomer. In the polymerization of MAF, the rate and degree of polymerization were quite enhanced compared with MAM, and gelation occurred at low conversion. The content of the unreacted allylic double bonds of the MAF polymer was quite large; whereas those of the unreacted fumaric double bonds and the cyclic structural units showed reverse tendencies. Only a slight presence of a five-membered ring was observed in the MAF polymer. The cyclization constants K_A and K_V, the ratios of the rate constants of the unimolecular cyclization reaction to those of the bimolecular propagation reaction of the uncyclized allylic and fumaric radicals, were estimated to be 2.73 and 1.48 mole/liter, respectively. These values suggest the great difference in the cyclopolymerization behavior between two isomeric monomers. These results are discussed in detail in connection with the high reactivity of the fumaric double bond compared to the maleic double bond. In addition, the formation mode and the sequence distribution of the structural units of the polymer produced are discussed on the basis of these analytical results. Thus, for the MAF polymer obtained in the bulk polymerization, about 60% of the cyclic structure can be formed via the intramolecular attack of the uncyclized fumaric radical on the allylic double bond, as opposed to the case of MAM via the predominant intramolecular attack (ca. 90%) of the uncyclized allylic radical on the maleic double bond; these results and the low probability for the succession of cyclic structures and the rather high probability of a vinyl-to-vinyl addition are presented.     

Magnitude and directionality of interaction in ion pairs of ionic liquids: relationship with ionic conductivity

The intermolecular interaction energies of nine ion pairs of room temperature ionic liquids were studied by MP2/6-311G level ab initio calculations. The magnitude of the interaction energies of 1-ethyl-3-methylimidazolium (emim) complexes follows the trend CF(3)CO(2)(-) > BF(4)(-) > CF(3)SO(3)(-) > (CF(3)SO(2))(2)N(-) approximately PF(6)(-) (-89.8, -85.2, -82.6, -78.8, and -78.4 kcal/mol, respectively). The interaction energies of BF(4)(-) complexes with emim, ethylpyridinium (epy), N-ethyl-N,N,N-trimethylammonium ((C(2)H(5))(CH(3))(3)N), and N-ethyl-N-methylpyrrolidinium (empro) are not very different (-85.2, -82.8, -84.6, and -84.4 kcal/mol, respectively), while the size of the orientation dependence of the interaction energies follows the trend emim > epy approximately (C(2)H(5))(CH(3))(3)N > empro. Comparison with the experimental ionic conductivities shows that the magnitude and directionality of the interaction energy of the ion pairs play a crucial role in determining the ionic dissociation/association dynamics in the ionic liquids. The electrostatic interaction is the major source of attraction between ions. The induction contribution is small but not negligible. The hydrogen bonding with the C(2)-H of imidazolium is not essential for the attraction in the ion pair. The interaction energy of the BF(4)(-) complex with 1-ethyl-2,3-dimethylimidazolium (em2im) (-81.8 kcal/mol) is only 4% smaller than that of the emim complex.     

ESR study of the photo-induced decomposition of polypropylene in the presence of N,N,N′,N′-tetramethyl-p-phenylenediamine

The mechanism of uv (λ > 325 nm) photodegradation of polypropylene (PP) containing N,N,N′,N′-tetramethyl-p-phenylenediamine (T₄MPD) has been investigated by means of ESR spectroscopy. The observed spectra after uv irradiation of both isotactic-PP (IPP) and stereoblock-PP (SPP) samples in vacuum at 77 K consisted principally of a broad singlet which was assigned to a T₄MPD cation radical (T₄MPD^+·). On the other hand, the spectrum observed after irradiation of an atactic polypropylene (APP) sample at 77 K in vacuum was resolved into several components which decayed almost up to ca. 263 K to give rise to the broad singlet of T₄MPD^+·. One component was a sharp quartet which was assigned to a methyl radical, ·CH₃·. The other component, a singlet, was attributed to a trapped electron, e_t^?.By comparison of the ESR spectrum of deuterated T₄MPD with that of the normal compound it was found that 60 ～ 70% of the methyl radicals arose from the added T₄MPD due to β-scission, which also formed the N,N,N′-trimethyl-p-phenylenediamine radical, T₃MPD·. The T₃MPD· radical presumably captures an electron at lower temperatures to become a carbanion, T₃MPD^?, which releases the electron to reproduce the T₃MPD· radical at elevated temperatures. This production of the radical T₃MPD· due to the liberation of an electron provides an explanation for the observed increase in intensity of the decay curve in the temperature range from ? 168 K to 185 K. The remaining fraction, 30 ～ 40%, of the total methyl radicals was produced from the PP matrix by an energy transfer from the excited T₄MPD¹ to the PP matrix. The broad singlet which appeared in the temperature range near 195 K was attributed to an acyl radical ～CH₂CH(CH₃)CH₂?O from the observed g-value. By photoillumination of this sample this broad singlet was converted reversibly into the quartet which was assigned to the radical ～CH₂CH(CH₂·)CH₂CHO.     

Separation of stereoisomers of some terpene derivatives by capillary gas chromatography-mass spectrometry and high-performance liquid chromatography using beta-cyclodextrin derivative columns

Gas chromatographic separations of the stereoisomers of menthol derivatives, important intermediates in the synthesis of physiologically active natural products, were carried out on several substituted beta-cyclodextrin (CD) columns, including per-O-methyl-beta-cyclodextrin (PME-beta-CD), heptakis(2,3-di-O-acetyl-6-tert-butyldimethylsilyl)-beta-CD (DIAC-6-TBDS-beta-CD), and heptakis(2,3-di-O-methyl-6-tert-butyldimethylsilyl)-beta-CD (DIME-6-TBDS-beta-CD) as chiral stationary phases (CSPs). With the DIME-6-TBDS-beta-CD column, a separation of the Z- and E-isomers of methylidenementhol was accomplished; no separation was achieved with the other columns. The stereoisomers of methylidenementhol and the corresponding tert-butyldimethylsilyl (TBS) ether were separated on both the beta-CD and the heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TME-beta-CD) columns by high-performance liquid chromatography (HPLC) with a mobile phase involving acetonitrile and H(2)O. For the separation of the Z- and E-isomers of methylidenementhol, the TME-beta-CD column was superior. In contrast, the beta-CD column was preferable in the case of the corresponding TBS ether.     

The molecular structure and chemical reactivities of the condensation products of o-substituted benzylidenacetylacetone with hydrazine dihydrochloride

Reaction of o-nitrobenzylideneacetylacetone ( 1a ) with hydrazine dihydrochloride in methanol gave 4-(α-methoxy-o-nitrobenzyl)-3,5-dimethylpyrazole hydrochloride ( 4a ), whose structure was unambigously confirmed by an X-ray crystallographic analysis, via 4-(o-nitrobenzylidene)-3,5-dimethylisopyrazole ( 2a ). Compound 2a was synthesized by condensation of 1a with hydrazine dihydrochloride in acetonitrile. Analogously the corresponding o-chloro derivatives ( 2b, 4b ) were obtained. These were converted to N-methyl ( 6b ) and N-acetyl ( 7a,b ) derivatives and the behaviors on bromination and pyrolysis were investigated.     

Macromolecular chirality induction on optically inactive poly(4-carboxyphenyl isocyanide) with chiral amines: a dynamic conformational transition of poly(phenyl isocyanide) derivatives

Optically active polyisocyanides (poly(iminomethylenes)) have been prepared with much interest in developing new functional materials. Polyisocyanides have been considered to have a stable 4(1) helical conformation even in solution when they have a bulky side group. However, the conformational characteristics of poly(phenyl isocyanide) (PPI) derivatives are still under debate. We now report that an optically inactive PPI derivative, poly(4-carboxyphenyl isocyanide) (poly-1), shows optical activity in the polymer backbone induced by external, chiral stimuli through acid-base interactions under thermodynamic control and exhibits induced circular dichroism (ICD) in the UV-visible region in DMSO. The ICD intensities of the poly-1-chiral amine complexes in DMSO gradually increased with time, and, in one case, the value reached 3 times that of the original value after 2 months at 30 degrees C. The conformational changes also occurred very slowly for poly-1 alone and its ethyl ester with time on the basis of (1)H NMR spectroscopic analysis. These results indicate that PPIs bearing a less bulky substituent may not have a 4(1) helical conformation but have a different type of prochiral conformation, for instance, an s-trans (zigzag) structure which may transform to a dynamic, one-handed helical conformation when the PPIs have a functional group capable of interacting with chiral compounds. The mechanism of helicity induction on poly-1 through a dynamic conformational transition is discussed on the basis of the above results together with molecular dynamic simulation results for PPI.