Glass transition temperatures of poly N — (N — alkyl)—maleimides

Abstract

The glass transition temperatures (T,s) of a series of poly N-(n-alkyl) maleimides covering only the even members with side chains ranging in length from ethyl to n-octadecyl have been studied from room temperature to above T,. T,s and thermal quantities have been determined from the specific volume-temperature relations only for the higher (n = 8, 10, 12, 14, 16 and 18, where n = n o of CH2) members of the series. However for the lower ones (n = 2 , 4 , 6 , 8 and 10) T,s have been detected from heat capacitytemperature traces of differential scanning calorimetry diagrams by extrapolation to zero rate of heating. Accurate consistency was found in the values (n = 8 and 10) determined by both experimental methods. T,s of these polymers continuously decrease as the number of methylene groups in the side chain is increased, and they have been correlated with the size of the n-alkyl group in the side chain. The results are in accord with a previously studied series concerning the effect of a long side chain on the T, of a comb-like polymer in the amorphous state. T,s of poly N-(n-alkyl) maleimides encompassing a wide range of methylene group content (n = 2 , 4 , 6 , 8 , 10 and 12) have been examined according to the Gordon-Taylor-Wood extrapolation with the objective of ascertaining the T, of polyethylene (PE). Our approach of ignoring higher members of the homologous series in this extrapolation appears to be old and well known and it has been variously ascribed to d i f p n t authors. Extrapolation of T, values t o 100% amorphous PE gives a T, of 200 f 10 K in complete agreement with recent predictions made by Boyer from different sources of data.The Simha-Boyer free volume quantity Au . T, decreases slowly with the methylene group content in the longer terms (n = 8, 10, 12, 14, 16 and 18) of the series presumably because of a reduction in the polarity or an in-chain crankshaft loss mechanism which generates free volume in the glassy state, as stated by Boyer. T,s do not correlate very well with the contributions of the atomic groups to the cohesive energy density (c.e.d.) so it can be concluded that c.e.d. is not the only factor determining T,. However, a somewhat improved relationship might be obtained by taking into account the steric hindrance effect according to an approach made by Hayes.

Synthesis, characterization and properties of N‐maleimide side‐chain liquid crystalline copolymers

“…The jump may be tentatively rationalized in terms of: (i) an artefact; it is interesting to note that the width of the trace associated to the T g increases with decreasing mesogen content. However, we have used the same protocol62 through all the series to define T g , therefore it would only produce an additional but continuous drift and not a jump. (ii) An abrupt change in the smectic field (SF) as a result of a change in concentration of the n ‐octadecyl side‐chains within the non‐mesogenic comonomer in the neighborhood of the mesogenic moieties.…”

“…T Cl and T m were taken to be at the maxima of the endotherms. Glass transition temperatures were located at the middle of the change in the heat capacity trace 62. All copolymers and two homopolymers samples were submitted to the same thermal history, that is, after the first heating scan, the samples were then annealed at 10 K above the isotropic temperature for 10–15 min.…”

Thermodynamic studies on poly[N-(n-octadecyl)maleimide] (PMI-18)/solvent systems by inverse gas chromatography with capillary columns

“…In making a crude assumption, the viscosity for a rigid noninteracting sphere model is = 26.69 1/2 1/2/ 2 (24) where = hard-sphere diameter in angstroms. Values of for nonpolar molecules can be calculated from the relation of to critical constants through the equation = (2.44 -u'HT'/PJ1'* (25) where ' is the acentric factor which is defined as51 ' = 0.006R + 0.02087 2 -0.00136 3 (26) and R is the radius of gyration in angstroms. Values for R were taken from Reid, Prausnitz, and Sherwood.…”

Synthesis and Thermal Properties of Comb‐Like Maleimide Copolymers Containing Polymethylene and Poly(Ethylene Oxide) Side Chains as the N‐Substituents

“…[15][16][17][18][19][20][21][22][23][24][25][26] The poly(RMI)s as the corresponding homopolymers with similar N-alkyl substituents were reported to exhibit high-T g values over the high temperature range from 97 °C for poly(ODMI) to 138 °C for poly(OMI). [27][28][29] The poly(RMI-alt -IB)s containing a long-alkyl side-chain exhibited the crystallization of their side groups, and consequently, the melting temperatures ( T m ) were observed of methanol and diethyl ether to precipitate the copolymer of the RMIs and PEGMI, respectively. The copolymers were fi ltered out, washed, and then dried in vacuo.…”

“…increase in the T g values of the obtained copolymers, but simultaneously it induced another problem of the brittleness of the copolymers. Previously, Barrales-Rienda and co-workers [ 27,28 ] and Matsumoto et al [ 29 ] reported that the T g values decreased according to an increase in the carbon number of the N-n -alkyl groups of the poly(RMI)s. Furthermore, it was pointed out that the semifl exible mainchain suppressed side-group crystallization due to their restricted mobility of the segments, [29][30][31][32] while the side alkyl chains introduced into common comb-like polymers with a fl exible main-chain readily crystallized accompanying the reconstruction of main-chain conformation. [33][34][35] In this study, we synthesized maleimide copolymers with a low-T g value by the introduction of fl exible and linear substituents into the side groups and characterized the thermal and viscoelastic properties of the copolymers consisting of a rigid main-chain and fl exible side chains.…”