Synthesis, Thermal Properties, and Gas Permeability of Poly(N-n-alkylmaleimide)s

Abstract

ABSTRACT:Radical polymerization of N-n-alkylmaleimides (nRMI) with various n-alkyl groups (n = 4--18) was carried out in the presence of 2,2' -azobisisobutyronitrile in benzene at 60°C.The high molecular weight polymer (M.> 10 5 ) was obtained in a high yield from all nRMis. The resulting poly(nRMI) were soluble in organic solvents such as benzene, chloroform, and THF, and a thin and tough film was obtained from the solution. It was confirmed that poly(nRMI) showed excellent thermal-stability, i.e., they had a high glass transition temperature and decomposition temperatures. The side-chain crystallization was investigated by differential scanning calorimetry. From the measurement of permeation of oxygen and nitrogen through poly(nRMI), it was revealed that these polymers had a high permeability coefficient of 10-8 -10-9 cm 3 (STP)cmcm-2 s -1 cm Hg-1 , which depended intensively on the N-substituents. KEY WORDS N-n-Alkylmaleimide / Radical Polymerization / Poly(substituted methylene) / Thermal Stability / Glass Transition Temperature / Side-Chain Crystallization / Differential Scanning Calorimetry / Gas Permeability / It has been reported since 1981 that dialkyl fumarates (DRF) with bulky ester alkyl groups underwent radical high polymerization to give high molecular weight polymers consisting of a poly(substituted methylene) structure. 1 • 2 These polymers have a less-flexible structure on account of a defect of a flexible methylene group as a spacer in the main chain, so that they have different properties from flexible ordinary vinyl polymers, i.e., poly(monosubstituted ethylene )s and poly(l, 1-disubstituted ethylene)s. 2 -4 For example, poly(DRF)s bearing bulky alkyl groups such as isopropyl or tert-butyl group do not show any glass transition temperature (Tg) and not melt under their decomposition temperatures. Furthermore, these rigid vinyl polymers have been expected to be applied as a new polymeric material for separation of gases, e.g., an oxygen enrichment membrane. 5 • 6 In general, gases such as oxygen and nitrogen permeate in rubbery polymers faster than glassy polymers, 7 • 8 but mechanical strength is also an important factor at the same time. Therefore, many efforts have been made for development of a new glassy polymer with high permeability. Poly(l-trimethylsilyl-1-propyne) has been reported to show the highest permeability coefficient, where a large unrelaxed volume in this glassy polymer is important for the high coefficient. 9 On the other hand, we have reported on radical polymerization of N-alkyl-substituted maleimides and N-(alkyl-substituted phenyl)maleimides bearing various alkyl groups, and the excellent thermal-stability of the resulting polymers. 10 -15 Recently, we found that N-n-alkylmaleimides (nRMI) polymerized readily as well as other maleimides to give high molecular weight polymer, and that the film of poly(nRMI) obtained showed high permeability for oxygen and nitrogen. 16 201

Polymerizability and Chiroptical Properties of the N-Substituted Maleimide Bearing L-Phenylalanine Alkyl Ester

“…This suggests that a long alkyl chain of the ester group in the N-substituent was favorable for the polymerizabilities of RMI. The tendency was identical with the radical polymerizations of RMI having N-alkyl chain reported by Matsumoto et al 15 That is, a long alkyl chain could not inhibit the propagation reaction but decrease the termination reaction because of high viscosity in the polymerization mixture. Consequently, it is considered that the polymerization reactivities were higher.…”

“…Consequently, it is considered that the polymerization reactivities were higher. 15 In anionic polymerizations of RPAM (lower paragraph in Table I in the radical polymerizations. Generally, there were little differences among the polymers in several solvents.…”

Gas Permeation through Poly(N-n-alkylmaleimide) Membranes

“…12 The amount of oxygen and nitrogen that permeated into the downstream side was determined by gas chromatography (Yanaco G 1800T). Commercial oxygen and nitrogen, or ambient air were used as a test gas at atmospheric, reduced, or increased pressure.…”

“…EXPERIMENT AL RMis were prepared by the methods described in the previous paper. 12 Other reagents and solvents were used after ordinary purification.…”

“…12 RESULTS AND DISCUSSION Figure l shows the dependence of the N-alkyl chain length on the permeability of oxygen and nitrogen through poly(RMI) membranes. It is clear that both P 02 and PN 2 increase when a longer alkyl chain is introduced into the side chain of poly(RMI), suggesting that the permeation rate of the penetrants through a domain of the alkyl side chains is important compared with that through the neighborhood of the main chain of the polymaleimides.…”