Bernard Meurer

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.

The structure and morphology of vinylidene fluoride and trifluoroethylene copolymers studied by wide-line nuclear magnetic resonance

Abstract Both hydrogen and fluorine nuclear magnetic resonance measurements have been performed on copolymers of vinylidene fluoride (VF 2 ) and trifluoroethylene (TrFE) containing from 30 to 100 mol% VF 2 . The temperature study of the 70 30 copolymer reveals that two crystalline and one amorphous phase must be considered to describe the ferroelectric transition. At low temperature, the structural change from α to β crystalline form with increasing TrFE content is clearly detected. At room temperature, the morphology of VF 2 -rich copolymers is well analysed with two components having the same 1 H to 19 F ratio. On the other hand, below 70 mol% VF 2 the two components have different 1 H to 19 F ratio, which implies segregation between TrFE-rich and VF 2 -rich sequences.

Solution properties of poly(vinylidene fluoride): 2. Relation between microgel formation and microstructure

Abstract In contrast to type I poly(vinylidene fluoride) (PVDF), solutions of type II PVDF contain, even in good solvents, a fraction of microgel that cannot be fully eliminated for characterization by light scattering. Intrinsic viscosity and size exclusion chromatography reveal that the soluble fraction has a molecular mass in the same range as type I samples, which are fully soluble in the same solvents. The shear moduli in the molten state reveal that the microgel fraction does not contain a high enough molecular mass to explain microgel formation by phase separation. From an analysis of the 19 F nuclear magnetic resonance spectra of both suspension- and emulsion-polymerized PVDF samples, with first-order Markov statistics, microgel formation is attributed to differences in microstructure, involving sequences with two reversed additions in a row.

High pressure effect on molecular motions in the paraelectric phase of a vinylidene fluoride and trifluoroethylene copolymer (7030) studied by n.m.r.

Abstract The 19 F n.m.r. spin-lattice relaxation times in both the laboratory and the rotating frame have been measured in a 70 30 mol % random copolymer of vinylidene fluoride and trifluoroethylene, over a range of pressures from 0.1 to 200 MPa in the paraelectric phase. Molecular motions have been investigated in this condis phase, and correlation times were obtained as a function of pressure and temperature. Activation parameters have been determined and discussed in terms of a thermally activated model and compared with literature data.

Matrix polarity effects on microphase separation in zwitterionomers, 2. Structural analysis of the model random zwitterionomers

Matrix polarity effects on the potential microphase separation in zwitterionomers were analyzed on four homologous series of model zwitterionic A i B copolymers. They combine in their chain various A i units -CH 2 -CH(CH 2 R i )-O- of finely tuned polarity such as epichlorohydrin (PEC, R i =Cl), glycidol (PGOH, R=OH), glycidyl acetate (PGAC, R i =O-CO-CH 3 ) or glycidyl p-nitrobenzoate (PONB, R i -O-CO-C 6 H 4 -NO 2 ) and highly dipolar and constant B units -CH 2 -CH[-CH 2 -O-(CH 2 ) 2 -N + (C 2 H 5 ) 2 -(CH 2 ) 2 -O-CO-C - (CN) 2 ]-O- of the ammonioethoxydicyanoethenolate type (μ = 25.9 D, molar transtion F n < 0.3). The bulk structure of the varions zwiterionomers was analyzed by differential scanning calcrimetry (glass transitions) and solid state NMR CH dipolar line shape analysis, chain dynamics) and correlated with the solubility properties of a model zwitterion in a series of solvent models of the various polymetic matrices (A i ) n . a) PGOH zwitterionomers are monophasic (one T g between 3 and 31°C) as a result of specific A-B hydrogen bonding, b) PGNB zwitterionomers are likely monophasic (one T g around 58°C) as a result of strong dipolar and dispersion A-B interactions but this feature cannot be definitely ascertained because of the too close glass transitions of the parent homopolymers c) The PEC zwitterionomer of F B = 0.11 is a biphasic material characterized by a quasi-quantitative segregation of the dipolar units in the hard phase (high T g ≃ 22°C) and a segregation case of PFC units in the soft phase (low T g ≃ -18°C) of about 84%. d) PGAC zwitterionomers are monphasic (one T g between -12 and 15°C), despite larly close and weak Van der Waals A-B interactions and study simular matrix mobility when compared to the previous PEC case. Thus, microphase separation in model A.B random zwitterionomers appears very sensitive towards small variations of the matrix polarity and of the A-B interactions.

Characterization of human aortic collagen's elasticity by nuclear magnetic resonance

The elasticity of the human aortic wall in longitudinal uniaxial elongation at high strain, known to be determined mostly from tissular collagens behaviour, is studied and compared to the second moment of the 1H nuclear magnetic resonance (NMR) solid state line-shape, a proton nuclear magnetic resonance (at 60 MHz) characteristic for the molecular motion and the rigidity of the collagen macromolecular backbone. The 1H NMR signal of collagen is identified after selective histologically controlled chemical lysis. The computed second moment of the line-shape shows statistically significant correlation with the slope of the strain-stress curve of the aorta at high strain, thus proving the relationship between a macroscopic tissular elasticity parameter and a macromolecular rigidity characteristic of collagen, a major tissular component. In vivo extension of this technique (e.g., MRI) would allow us to gain information on the biomechanical state of the aorta, a naturally highly stressed and strained tissue.