Monique Galin

Poly(sulphopropylbetaines): 3. Bulk properties

The bulk properties of a series of five atactic aliphatic and aromatic poly(sulphopropylbetaines) have been studied by u.v. and broad line n.m.r. spectroscopy, differential scanning calorimetry (d.s.c.), X-ray scattering (WAXS, SAXS) and thermally stimulated depolarization currents (t.s.d.c.). The high density in dipolar units N+(CH2)3SO−3 affords a number of specific properties to these poly(zwitterions): very high glass transition temperatures (d.s.c., n.m.r.); (ii) a strong polarity typified by an apparent local dipole moment of about 5.5 D (u.v.) and a dielectric increment at Tg > 1 × 102 (t.s.d.c.); (iii) the ability to dissolve LiClO4 in stoichiometric amounts to yield amorphous microphase separated blends (WAXS, SAXS) without much change in chain dynamics (slight increase in Tg and in n.m.r. linewidth); (iv) a very high affinity for water which behaves as a very efficient plasticizer with 6.5 moles of ‘unfreezable bound water’ per monomeric unit.

Poly(ammonioalkanesulfonate) Blends with Polar Organic Species and Alkali Metal Salts: Structure, Glass Transition and Ionic Conductivity

Because the dipole moment of its zwitterionic side group is very high (μ∼23 D), poly[3-(N,N-diethyl-N-(5-methacryloyoxy-3-oxopentyl)-ammonio) propanesulfonate] affords a unique polar host matrix possessing a strong solvation power towards a variety of polar or ionic guest species. Water, glycerol, liquid ethylammonium nitrate, triethylammoniopropanesulfonate are all good plasticizers with a fairly similar efficiency of ΔTg∼−2°C/mol% of additive, while a dizwitterion behaves as a weak antiplasticizer. The stoichiometric blends of the polyzwitterion with alkali metal salts of low enough lattice energy such as thiocyanates, trifuoromethanesulfonates, iodides, perchlorates, tetrafluoro or tetraphenylborates, are amorphous systems showing a single glass transition, with plasticization or antiplasticization effects depending on the salt nature. Microphase separation systematically occurs in these binary systems but long-range order is observed only in some cases, with development of lamellar (I−) or hexagonal (SCN−) structures. Conductivity increases and the dielectric constant of the material decreases as salt is added. The activation energies of the conductivity are not strongly affected either by the state of the material, glassy or viscoelastic, or by the salt nature.

Dielectric increments, intercharge distances and conformation of quaternary ammonioalkylsulfonates and alkoxydicyanoethenolates in aqueous and tirfluoroethanol solutions

ω-(Triethylammonio)alkane-α-sulfonates (H5C2)3N+–(CH2)n–SO3–(n= 2–4), pyridinio-, 2,6-lutidinio- and N-methylimidazolinio-propanesulfonates, and triethylammonioalkoxydicyanoethenolates (H5C2)3N+–(CH2)n–O–CO–C–(CN)2(n= 2, 3) have been studied by dielectric measurements (1 MHz–1 GHz) in dilute aqueous or trifluoroethanol solution. Their intercharge distances have been derived from their dipole moments (µ in the range 18–30 D) calculated according to Buckinghams theory, and compared with the maximum and minimum intercharge distances estimated by molecular mechanics for the ideal fully extended and ion-pair conformations respectively. For identical tether length, stronger charge delocalization in the cationic (imidazolinium versus pyridinium) or anionic (dicyanoethenolate versus sulfonate) sites slightly increases the intercharge distance, while better specific solvation of the zwitterions by hydrogen bonding in the less dissociating trifluoroethanol does not result in any significant conformational change with respect to aqueous solutions. Folding of the intercharge arm, negligible for 2-(triethylammonio)ethane-1 -sulfonate, progressively increases with its length, but the ion-pair conformation, where the intercharge distance becomes rapidly insensitive to the tether length, is never reached. This behaviour is in good agreement with the variations of the apparent ΔpKa values of the zwitterions (normalized to that of n-C4H9SO3H) measured by potentiometry in acetic anhydride-acetic acid (9:1, v/v) solution.

Thermodynamic studies on polyether—solvent systems by gas—liquid chromatography

Abstract The partial molar enthalpies of mixing at infinite dilution ΔH 1 ∞ of a series of 23 solvents (1), covering a fairly broad range of polarity, with liquid poly(ethylene oxide) and poly(tetramethylene oxide) (2) have been measured by gas—liquid chromatography over the range 70–140°C. The variations of ΔH 1 ∞ have been analysed in terms of probe structure through linear multiparametric correlations involving the molar volume V (or molecular refraction MR), the lowest unoccupied molecular orbital (LUMO) energy ϵL and the hydrogen-bond donating power α (Taft scale) as probe polarity descriptors. Statistically significant correlations are obtained, emphasizing that an exothermic mixing process arises essentially from negative contributions of the ϵL and α terms: the ether function of the chain behaves as an n-donor and as a hydrogen-bond acceptor. The positive contribution of the MR term is a direct measure of the cavitation effects: for the two polyethers, and polystyrene, poly(vinyl acetate) and poly(vinylidene fluoride) previously studied, the corresponding coefficients of the MR term are an increasing linear function of the cohesive energy density of the polymers as measured by the square of their Hildebrand solubility parameters δ2.

Gas−liquid chromatography study of the thermodynamics of interactions between linear polyethylene and non-polar and polar solutes

Abstract The thermodynamics of mixing at infinite dilution of a series of 25 low molecular weight aprotic solutes covering a broad range of polarity from n-alkanes to dimethylsulphoxide with molten linear polyethylene has been investigated by gas-liquid chromatography between 135 and 175°C. The lack of any specific solute-polymer interactions load to partial molar free energies and enthalpies of mixing at infinite dilution, ΔG ∞ 1 and ΔH ∞ 1 , are always positive. Quantitative analysis of the ΔG ∞ 1 and ΔH ∞ 1 variations with probe structure may be performed according to an empirical linear correlation ΔG ∞ 1 or ΔH ∞ 1 = f (μ 2 1 ), which acknowledges the influence of solute polarity through its dipole moment μ1 ( ΔH ∞ 1 =( KJ mol −1 )=1.43+0.48 (μ 1 × 10 30 ) 2 , R(25)=0.95 for instance). Alternatively, the Hildebrand-Scatchard equation, which acknowledges the influence of solute cohesion through its solubility parameter δ1 ( ΔG ∞ 1 N 1 or ΔH ∞ 1 V 1 =(δ 1 −δ 2 ) 2 , R(25)=0.90) and which makes it possible to derive a reliable value of the PE solubility parameter: β2=11.3 (J cm−3)0.5 at 140°C for instance. These two apparently different and successful approaches may probably rest on similar physical grounds because dipolar interactions are the major factor of solute cohesion for the population under investigation.

Free-Radical Copolymerization of Methyl Methacrylate and α-Methacrylophenone. I. Reactivity Ratios

Abstract The free-radical copolymerization of methyl methacrylate and methacrylophenone (MAP) initiated by azobisisobutyroni-trile at 60°C has been studied in ethylbenzene solution and in bulk. The process is characterized by a competitive Diels-Alder condensation of methacrylophenone and by a very low reactivity of methacrylophenone-terminated macroradicals in propagation reactions. The experimental composition data are consistent with a terminal unit model: rA = 1.77 ± 0.02, rB = 0.110 ± 0.006. Copolymerization with depropagation of methacrylophenone-terminated growing chains and copolymerization affected by penultimate effects have been tested as optimized possible models to take into account the inability of MAP to undergo homopolymerization.