This paper, second in a series, reports the cationic polymerization of 3-ethyl-3-(hydroxymethyl)oxetane leading to branched polyethers containing exclusively methylol groups attached to the quaternary carbon atoms (primary hydroxyl groups). GPC chromatograms and MALDI TOF spectra of the isolated polymers demonstrated that intramolecular chain transfer to polymer occurred, providing a cyclic fragment of the macromolecule. This limited the chain growth and thus the molecular weight of resulting polymers. The phosphorus cation-trapping method showed that both secondary and tertiary oxonium ions were present in the polymerization mixture, indicating that both active chain end (ACE) and activated monomer (AM) mechanisms contributed to the chain growth. As a consequence of the coexistence of two propagation mechanisms and significant chain transfer, both molar mass and degree of branching depended only slightly on the polymerization conditions.
SUMMARY: Poly(oxyethylene)s terminated at both ends with 2-bromopropionate end-groups were prepared and characterized by means of MALDI TOF mass spectrometry. It was shown, that atom transfer radical polymerization (ATRP) of methyl methacrylate with a poly(oxyethylene) macroinitiator in bulk proceeds with low initiation efficiency while polymerization of tert-butyl acrylate proceeds with practically quantitative initiation, leading to ABA block copolymers. Originally formed tert-butyl acrylate blocks contain terminal bromine, as expected for the ATRP mechanism. MALDI TOF analysis indicates, however, that in the later stages of polymerization side reactions lead to elimination of terminal bromine.
Cationic copolymerization of tetrahydrofuran (THF) with ethylene oxide (EO) in the presence
of diols proceeds with simultaneous participation of secondary and tertiary oxonium ions. This process
comprises therefore some features of the activated
monomer (AM) and the active
chain
end (ACE)
mechanisms. The mechanism of copolymer formation was evaluated, and the kinetics of competing
reactions involving both secondary and tertiary oxonium ions with nucleophiles present in the system
was studied. The apparent rate constants were derived, allowing the estimation of the influence of
copolymerization conditions on the composition and microstructure of copolymers.
Phthalic acid esters are important additives in polyvinyl chloride (PVC) products. Since PVC plastisoles for the production of wallcoverings contain about 30% phthalic acid esters, it is a crucial question whether these products can contribute to the pollution of the indoor environment. In this study, the emission of several technically relevant phthalates from PVC-coated wallcoverings were measured in emission test chambers under standard room conditions. During a 14-day test period, both the chamber air concentrations and the condensation on a cooled plate (fogging) were determined. In the chamber air, maximum concentrations of 5.1 micrograms/m3 for di-n-butylphthalate (DBP), 2.08 micrograms/m3 for di-pentylphthalate (DPP) and 0.94 microgram/m3 for di-(2-ethylhexyl)phthalate (DEHP) were found. After 14 days of exposure, up to 60.4 micrograms DEHP and 17.7 micrograms DPP could be quantified on the cooled plates of the fogging apparatus. The amounts of DBP and DIBP were significantly lower. A simple exposure calculation indicated no specific risk of an increased phthalate exposure in rooms with PVC wallcoverings.
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