Template molecular weight effects on the polymerization of acrylic acid

Acrylic acid was polymerized in dilute aqueous solution in the presence of a series of polyvinylpyrrolidones (PVP) of different molecular weight. Both inhibition time and rate of polymerization increased with PVP molecular weight. Purification of the PVP had no effect on these results. The complex produced by the polymerization was separated by methylation of the acrylic acid. The degree of polymerization ($\text{DP}$) of the polyacrylic acid formed in template polymerizaton was found to be remarkably similar to the $\text{DP}$ of the template PVP. A significant degree of isotacticity had also been induced in the PAA.     

The effect of ion energy upon plasma polymerization deposition rate for acrylic acid

A novel technique, which allows the importance of ion energy in plasma polymer film growth to be investigated, without perturbation of any other plasma parameter (particle densities or temperatures) or, in principle, perturbation of particle (neutral or ion) fluxes is applied in the plasma polymerisation of acrylic acid and new insight into polymer formation is gleaned.     

Continuous precipitation polymerization of acrylic acid in supercritical carbon dioxide: The polymerization rate and the polymer molecular weight

The precipitation polymerization of acrylic acid in supercritical carbon dioxide was studied in a continuous stirred tank reactor with 2,2′‐azobis(2,4‐dimethylvaleronitrile) as the free‐radical initiator. The reactor temperature was between 50 and 90 °C, the pressure was 207 bar, and the average residence time was between 12 and 40 min. The product polymer was a white, dry, fine powder that dissolved in water. A wide range of polymer molecular weights (5–200 kg/mol) was obtained. The effects of the operating variables on the polymerization rate and on the polymer molecular weight were evaluated. The observed kinetics suggested that polymerization took place in both the supercritical fluid and the precipitated polymer particles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2546–2555, 2005     

Polarizability of negative molecular ions

Theoretical and Experimental Chemistry -     

Radiation-induced polymerization of acrylic acid in aqueous solution

Aqueous acrylic acid in the presence of cupric chloride has been subjected to γ-irradiation under various reaction conditions and the molecular weights of the resultant poly(acrylic acid) measured. The results, taken in conjunction with previous findings on the dependence of the rate of polymerization on intensity, monomer concentration, and cupric chloride concentration, indicate chain termination solely by cupric ion (rate constant k_tCu) and chain transfer to polymer (rate constant kf). Values have been obtained for k_tCu/k_p, k_f/k_p and G(radical) of acrylic acid. On the basis of these data a theoretical chain-length distribution has been derived which agrees well with distribution measured by gel-permeation chromatography.     

Graft polymerization of acrylic acid onto powdered polyethylene

Radiation-induced graft polymerization of acrylic acid onto powdered polyethylene samples of various granulometric compositions was studied. The resulting graft polymer can be used as a cation-exchange sorbent. The ion adsorption properties of the synthesized cation exchanger were characterized.     

Hidden rearrangement processes in short-lived negative molecular ions

The study of resonant electron capture by nitrobenzene molecules showed that some fragmentary negative ions are unstable toward electron autodetachment. The measured appearance energy of the neutral component of an [M — H]⁻ ion beam does not agree with the energetics of direct dissociation in a molecular ion. The estimation calculations show that the low appearance energy of [M — H]⁰ neutral components is caused by isomerization of a molecular ion of nitrobenzene to the 2-nitrobenzene structure followed by the formation of a phenoxide ion in the autodetachment state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 367–370, February, 2006.     

Surface modification of non-woven fabric by DC pulsed plasma treatment and graft polymerization with acrylic acid

Direct-current pulsed plasma treatment (DPPT) followed by thermal-induced graft polymerization with acrylic acid (AA) was used to modify poly(ethylene terephthalate)/polyethylene (PET/PE) non-woven fabric (NWF) in this study. The water contact angle of plasma modified NWF decreased sharply with DPPT time in 4 s. The water content of the NWF increased with DPPT time and levelled off after 30 s. Chemical analysis by X-ray photoelectron spectroscopy (XPS) indicated that the surface property of modified NWF could be maintained for more than 8 months under ambient conditions and could be further improved by grafting with acrylic acid. The concentration of AA in PET/PE-g-AA NWF increased both with the monomer concentration and the plasma treatment time. The maximum grafting density was 1.17 μmol/cm² with 40 s DPPT and 20% (w/w) AA. Improved biocompatibility of the modified NWF was confirmed with 3T3 fibroblast cells where cell viability was analyzed by MTT assays. More cells were found to attach to the modified NWF with higher growth rates, indicating that an improvement in surface properties by DPPT followed by graft polymerization of AA is beneficial for cell attachment and growth. A much more uniform cell distribution was found within the modified NWF from confocal laser scanning microscope observations.     

Inhibition of acrylic acid polymerization by phenothiazine and p-methoxyphenol

The major features of polymerization induction periods for acrylic acid inhibited with phenothiazine and p-methoxyphenol have been characterized at 100°C, including duration of the induction periods, and rates of inhibitor disappearance, molecular oxygen absorption, and peroxide formation. Surprisingly, thermally produced radicals react more rapidly with phenothiazine than with oxygen since there is no detectable oxygen absorption or peroxide for mation during phenothiazine-induced induction periods. Thus, phenothiazine has been used to estimate the thermal rate of radical formation. Phenothiazine's effectiveness as an inhibitor is not directly affected by oxygen, although it does undergo oxygen-promoted, noninhibition-related side reactions. p-Methoxyphenol, on the other hand, depends entirely on the presence of oxygen to function as an inhibitor. Compared with equivalent concentrations of p-methoxyphenol, induction periods obtained with phenothiazine are very long, and the rate of inhibitor disappearance is slower by at least an order of magnitude. The characteristics of p-methoxyphenol inhibition reflect a greater radical flux deriving from the significant rates of oligomeric peroxide formation and decomposition which we measured during p-methoxyphenol-induced induction periods at 100°C. MEHQ is an effective inhibitor at ambient temperatures in part because of the greater stability of the peroxides at these lower temperatures.     

Grafting polymerization of acrylic acid onto preirradiated polypropylene fabric

Acrylic acid (AAc) was grafted onto polypropylene (PP) fabric by a preirradiation method using a Co-60 gamma ray. The effect of absorbed dose, AAc concentration, reaction temperature, reaction time, storage time, as well as the effect of ferrous ion and sulfuric acid on the degree of grafting were determined. It has been shown that the synergistic effect of sulfuric acid with the ferrous sulfate can not only increase the grafting yield, but also decrease the apparent activation energy for the grafting. It leads to the possibility of getting a particular grafting yield at a lower absorbed dose. In this experiment, It has also been shown that the grafting activity of preirradiated PP fabric in AAc aqueous solution could be well kept at room temperature for a long period.     

Photoelectron imaging of negative ions: atomic anions to molecular clusters

The negative ion photoelectron imaging technique is illustrated using two relatively simple atomic and molecular anion systems, and then applied to the study of a cluster system. Photoelectron images of I- and CS2- at 267 nm and 800 nm respectively are presented. Photoelectron spectra and angular distributions are obtained from the images and the concepts underlying these and their interpretation are outlined. The imaging technique is then applied to (CS2)n - (n = 2-4) cluster anions, for which 400 nm images are presented. Features of these images are highlighted and discussed with reference to solvation effects and structural properties of the cluster anionic moiety. Photoelectron signatures of different forms of the cluster core are discussed. These core structures are anionic monomer units solvated by the remaining n - 1 CS2 molecules or covalent dimer units solvated by the remaining n - 2 molecules. Images of the n = 2 anion at 400, 530 and 800 nm reveal information about the electron detachment processes within the different cluster types and both direct detachment and autodetachment are seen. The direct transitions are seen from clusters with either core type, while autodetachment is only seen from clusters with the covalent dimer core. The imaging work also reveals evidence of a previously unreported electronic transition within the direct detachment band due to the covalently bound core type.     

A survey of some theoretical studies of negative ions

The quantum chemical methods employed by us to investigate the stabilities, charge densities, and bonding characteristics of atomic and molecular anions are briefly reviewed. The results of our work on chemically interesting species are surveyed, as are our initial results on the treatment of solvation effects in anionic systems. Finally, a simple-minded approach to the problem of finding shape resonances for electron–atom scattering processes is outlined.     

Mass spectra of the negative ions of some steroids

It has been shown that the main directions of the fragmentation of the molecular negative ions are connected with the formation of systems of conjugated bonds and the delocalization of the negative charge over a π-system of electrons. The mass spectrometry of the negative ions formed by the dissociative capture of electrons (DCE) is promising for the study of the molecules of steroid compounds.     

Rearrangement processes in gas-phase negative ions. 1. Difluorocinnamic acid and some other organofluorine compounds

Rearrangement processes with the successive splitting out of HF and CO₂ molecules, the contribution of which to the scheme of the fragmentation of the negative molecular ions reaches 99%, are realized in the resonance capture of thermal electrons by molecules of organofluorine compounds (derivatives of di- and tetrafluorocinnamic acids and 1,4-diaryltetrafluorobutadiene).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1547–1549, July, 1990.