Effect of 2-Chloro-1,3,2-dioxaphospholane on the radical polymerisation of acrylonitrile, styrene and methyl methacrylate
TL;DR: In this paper, the effect of 2-Chloro-1,3,2-dioxaphospholane on the AIBN initiated polymerisation of acrylo was investigated kinetically in benzene at 60 − 80°C.
Abstract: The effect of 2-Chloro-1,3,2-dioxaphospholane on the AIBN initiated polymerisation of acrylo — nitrile , methyl methacrylate and styrene was investigated kinetically in benzene at 60 – 80°C. With acrylonitrile normal kinetic orders with respect to monomer and AIBN could be observed with the phospholane behaving as a chain transfer agent. With methyl methacrylate and styrene it was observed that the phospholane causes enhancement of the rates due to concurrent radical and ionic polymerisation besides functioning as a chain transfer agent.
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TL;DR: In this paper, a 6-311G basis set was used to study the energy properties of oxides, sulfide, and selenide at the DFT/B3LYP level and several ab initio methods.
Abstract: 2-Chloro-1,3,2-dioxaphosphorinane-2-oxide, -sulfide, and -selenide are studied at the DFT/B3LYP level and several ab initio methods using a 6-311G** basis set. Our energy optimizations by all these methods show that for oxide DFT and ab initio methods are not much different, while for the sulfide and the selenide the DFT relative energies are higher by about a kcal/mol as compared to those of MP2, MP3, MP4(SDTQ)//MP2, and CCSD(T)//MP2 (//MP2 indicates that a single-point calculation based on the MP2 optimized geometry is performed). However, regardless of rather large relative energies, that does not change the fact that in all three cases the conformational equilibrium mixture contains more than 95% of the lowest, chair-equatorial conformer (this indicates that the P=X bond is in equatorial position). This one and the next higher conformer (chair-axial) are confirmed to be real conformers (energy minima) in all cases. The energetically much higher twist and boat forms are probably just stationary states and local maxima because in many cases, geometry optimizations do not converge to them. Only for MP2 and the selenide do all optimizations converge to the desired stationary state. The relative energies could all be explained in terms of anomeric effects and ring strains. The decreasing covalent character of the P=X bond, with X changing from O to S and to Se, shows itself in the increasing bond lengths and the decreasing strength of anomeric effects.
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TL;DR: The structural stability and ring inversion of 2-chloro-1,3,2-dioxaphospholane 2-oxide and 2-sulfide were investigated by the DFT-B3LYP and the ab initio MP2 calculations with 6-311+G ∗∗ basis set as discussed by the authors.
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TL;DR: In this article, a 6-311G* basis set of 2-Chloro-1,3,2-dioxaphosphorinane-2-oxide, -sulfide, and -selenide was used for the assignment of symmetry coordinates.
Abstract: 2-Chloro-1,3,2-dioxaphosphorinane-2-oxide, -sulfide, and -selenide are studied with the help of DFT/B3LYP and several ab initio methods using a 6-311G** basis set. However, due to rather large relative energies of higher conformers in all three cases, the conformational equili-brium mixture contains more than 95% (see the preceding paper in this Journal) of the lowest chair-equatorial conformer (this indicates that the P=X bond is in the equatorial position), so we do not find any conformer bands in the experimental spectra and calculate our theoretical ones for the assignment only from the chair-equatorial conformer. The vibrational infrared and Raman spectra were calculated and are in fair agreement with their experimental counterparts. Potential energy distribution calculations are performed, and the theoretical modes where an experimental counterpart could be found to symmetry coordinates are assigned.
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TL;DR: Light scattering determinations of molecular weight and coil size made at room temperature with three different cells at two wavelengths of incident light and in two solvents (acetone and acetonitrile) on fourteen fractions and six whole polymers of polymethyl methacrylate ranging in molecular weight from 2.7 × 103 to 2.5 × 106 provide a basis for estimation of the validity and reliability of such measurements as mentioned in this paper.
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TL;DR: In this paper, the effect of polymerization temperature on the molecular conformation of polyacrylonitrile was investigated. But the results were not analyzed with aid of the recent viscosity theory of StOCKCMAYER and FIXMAN.
Abstract: Um den Einflus der Polymerisationstemperatur auf die Molekulformation des Polyacrylnitrils zu untersuchen, werden zwei Praparate bei zwei verschiedenen Temperaturen unter Verwendung eines Redoxsystems hergestellt. Die Molekulargewichte von sieben Fraktionen des bei −30°C hergestellten Polymerisates („T„-Reihe) und von sechs Fraktionen des bei +60°C gewonnenen („S„-Reihe) werden nach dem Ultrazentrifugen-Verfahren von ARCHIBALD bestimmt.
Zwischen der Viskositatszahl in Dimethylformamid (DMF) und dem Molekulargewicht gelten folgende Beziehungen:
Die Viskositatsgleichung fur die „S„-Reihe stimmt mit der von CLELAND und STOCKMAYER sehr gut uberein.
Die Mesdaten werden mit Hilfe der neuen Viskositatstheorie von STOCKMAYER und FIXMAN analysiert, um die ungestorten Knaueldimensionen der beiden polymerhomologen Reihen miteinander zu vergleichen. Die dieser Theorie entsprechende Form der [η]-M-Beziehung lautet fur die „S„-Reihe:
Es wird gefunden, das die ungestorte Knaueldimension der „S„-Reihe um etwa 10% kleiner ist als die der „T„-Reihe. Der sterische Faktor σ, der als Verhaltnis der ungestorten Knaueldimension zu der bei freier Drehbarkeit zu erwartenden definiert wird, liegt bei 2,10 fur die „S„-Reihe und bei 2,30 fur die „T„-Reihe. Dieser Tatsache wird entnommen, das der syndiotaktische Anteil des Polyacrylnitrils durch Erniedrigung der Polymerisationstemperatur vergrosert wird.
In order to study the influences of polymerization temperature upon the molecular conformation of polyacrylonitrile, two types of samples are prepared at two different temperatures using a redox system. By employing the ARCHIBALD ultracentrifugal procedure the molecular weight determination is made for seven fractions from a sample polymerized at −30°C. (“T”-series) and for six ones from that obtained a t +60°C. (“S”-series).
Between the intrinsic viscosity in dimethyl formamide (DMF) and the molecular weight the following relations are found:
The viscosity equation for the “5”-series is in good agreement with that of CLELAND and STOCKMAYER.
These results are analysed with aid of the recent viscosity theory of STOCKCMAYER and FIXMAN to evaluate the unperturbed dimension of these two homologous series. The [η]- M-relation for the “S”-series in the STOCKMAYER-FIXMAN form is:
The unperturbed dimension of the „S”-series is found to be smaller than that of the “T”-series. The steric factor σ, defined as the ratio of unperturbed dimension to that corresponding to the free rotation, is about 2.10 and 2.30 for the “S”- and “T”-series, respectively. This leads to the conclusion that the syndiotactic part in the chain of polyacrylonitrile will be increased by a lowering of the temperature of polymerization.
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