Under identical conditions of cationic polymerization at low temperature 2‐( p ‐tolyl)‐1‐propene (α, p ‐dimethylstyrene) gave polymers with much higher syndiotactic contents than unsubstituted α‐methylstyrene....
Under identical conditions of cationic polymerization at low temperature 2‐( p ‐tolyl)‐1‐propene (α, p ‐dimethylstyrene) gave polymers with much higher syndiotactic contents than unsubstituted α‐methylstyrene. All samples of poly(α, p ‐dimethylstyrene) were crystalline, but poly(α‐methylstyrene) did not crystallize even at high degrees of stereoregularity. Similarly polymers of p ‐isopropyl‐α‐methylstyrene were crystalline, and the crystalline properties of copolymers of the three monomers were investigated and compared to those of the homopolymers. The rôles of stereoregularity and crystallizability in forming crystalline products were considered. Unter identischen Bedingungen der kationischen polymerisation bei tiefer Temperature lieferte 2‐( p ‐Tolyl)‐1‐propen (α, p ‐Dimethylstyrol) polymere mit höherem syndiotaktischem Gehalt als das unsubstituierte α‐Methylstyrol. Sämtliche Proben von Poly(α, p ‐dimethylstyrol) erwiesen sich als kristallin im Gegensatz zum Poly(α‐methylstyrol), das selbst bei hoher Stereoregularität nicht kristallisierte. Ähnlich erwiesen sich polymere des p ‐Isopropyl‐α‐methylstyrols als kristallin. Die kristallinen Eigenschaften von Copolymeren der drei Monomere wurden untersucht und mit denen der Homopolymere verglichen. Die Rolle der Stereoregularität und der Kristallisierbarkeit bei der Bildung kristalliner Produkte wurde in Betracht gezogen.
The nature of the distribution of ionic groups in cesium salts of ethylene-methacrylic acid and ethylene-acrylic acid copolymers containing 2.1 to 6.3 mol% acid was examined using the small-angle and wide-angle x-ray ...
The nature of the distribution of ionic groups in cesium salts of ethylene-methacrylic acid and ethylene-acrylic acid copolymers containing 2.1 to 6.3 mol% acid was examined using the small-angle and wide-angle x-ray scattering techniques. The low-angle data containing a maximum characteristic of these materials were analyzed according to principles of small-angle scattering theory. The radial distribution functions for a typical salt and unionized copolymer were derived from the combined small- and wide-angle data. The results of these two approaches indicate the presence of ionic clusters of the order of 10–20 Å in size. There is evidence that these clusters are of spherical geometry. The low-angle maximum is interpreted as an interference resulting from short range ordering of ionic groups around ionic clusters.
We have studied the homogeneous hydrogenation of a series of unsaturated polymeric substrates with diimide formed from the thermal decomposition of p ‐toluenesulfonylhydrazide (TSH) at elevated temperatures (110 to 1...
We have studied the homogeneous hydrogenation of a series of unsaturated polymeric substrates with diimide formed from the thermal decomposition of p ‐toluenesulfonylhydrazide (TSH) at elevated temperatures (110 to 160°C) and in aromatic solvents. At a TSH/olefin ratio of 2.0, homopolymers of butadiene, polycyclohexadiene, and polyisoprene were quantitatively hydrogenated as were two styrene/butadiene copolymers. Alkyl branching at or near the residual polymer double bond, as in methyl rubber and poly‐2.5‐dimethyl‐2.4‐hexadiene, gave less than 50% hydrogenation. Polychloroprene was not hydrogenated by diimide (conversions less than 10%) which is in agreement with the behavior previously observed for low molecular weight olefins. The unsaturated polymers which were successfully hydrogenated were soluble and, hence, showed no excessive crosslinking. Polycyclohexadiene and polyisoprene, the only samples evaluated for molecular weight changes, exhibited no chain degradation. Some qualitative kinetic data were obtained using per cent conversion vs. time data. Under the conditions of toluene reflux and TSH/olefin ratios of 1.5, the relative rates of hydrogenation for cis, trans and vinyl butadiene units was k cis ≃ k trans < k vinyl. Byproducts from the diimide generation resulted in the introduction of 0.2 to 1.0% of p ‐CH 3 C 6 H 4 SO 2 ‐groups into the polymer based upon 100% of the double bonds originally present. Die homogene Hydrierung einer Serie ungesättigter polymerer Substrate mit Diimid, dargestellt durch Thermolyse von p ‐Toluolsulfonylhydrazid (THS) bei 110–160°C, wurde in aromatischen Lösungsmitteln untersucht. Bei einem TSH/Olefin‐Verhältnis von 2,0 wurden sowohl die Homopolymeren des Butadiens, das Polycyclohexadien und das Polyisopren, als auch zwei Styrol/Butadien‐Copolymere quantitativ hydriert. Bei Alkylverzweigung an oder in Nachbarschaft der Doppelbindung des polymeren, wie im Poly‐2.5‐dimethyl‐2.4‐hexadien, verlief die Hydrierung zu weniger als 50%.
Temperature dependent infrared studies have been carried out on three series of poly-urethanes previously synthesized and characterized. The repeat units of the three series may be schematically represented as follows...
Temperature dependent infrared studies have been carried out on three series of poly-urethanes previously synthesized and characterized. The repeat units of the three series may be schematically represented as follows: In each case n varies from 2 to 10. The H and DP series are partially crystalline while the 4M series is entirely amorphous. It was possible to draw several conclusions concerning the hydrogen bonded NH and Cbond;O groups in these polymers. These conclusions are: (1) The aromatic polyurethanes of the DP and 4M series are hydrogen bonded in the amorphous phase below the glass transition temperature, (T g ) , to the extent of 75% or less whereas the aliphatic H series is completely hydrogen bonded below T g . (2) Both the DP and H series are completely hydrogen bonded in the crystalline phase below the melting point, ( T m ), regardless of the value of n . (3) A temperature dependent equilibrium between free and hydrogen bonded NH groups occurs in the amorphous phase above T g in all three series. (4) The temperature dependences of the total area of the NH stretching bands exhibit transitions corresponding to T g , T m , and, in the case of the H series, to a first order crystal-crystal phase transition, T t . (5) The temperature dependences of the frequencies of the hydrogen bonded NH stretching vibration also exhibit transitions corresponding to T g and T m .
暂无评论