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This paper deals with the determination of the main characteristics and the assignment of the molecular motions leading to the solid-state transitions observed in amorphous polymers at temperatures lower than the glass--rubber transition. First, the specific features of these secondary transitions (β, γ, δ, ...) are briefly described. Then, the behaviour of various polymer systems is analysed: poly(cycloalkyl...
The use of semi-hydrolyzable oligoester-derivatized interpenetrating polymer networks (IPNs) as nanostructured precursors provides a straightforward and versatile approach toward mesoporous networks. Different poly(d,l-lactide) (PLA)/poly(methyl methacrylate) (PMMA)-based IPNs were synthesized by resorting to the so-called in situ sequential method. The PLA sub-network was first generated from a dihydroxy-telechelic...
13 C NMR in solution and molecular dynamics simulations were used to discuss the respective roles of intramolecular constraints and intermolecular contributions in poly(di-n-alkylitaconate)s (PDAI) with various side chain lengths. These polymers exhibit the unusual phenomenon of two distinct glass transitions when the alkyl side chains contain at least six carbon atoms. Nuclear Overhauser enhancement...
Scanning electron microscopy, solid-state proton NMR spectroscopy and static mechanical analysis have been performed in order to evaluate the compatibilising action of random copolymers of polystyrene and polybutadiene and triblock copolymers of poly(styrene–butadiene–styrene) in incompatible polystyrene/polybutadiene (PS/PB) blends. Scanning electron microscopic examination of the cryofractured and...
The structure and rheological behavior of atactic poly(vinyl alcohol) (a-PVA) hydrogels prepared by freeze/thaw cycles were investigated as a function of polymer concentration and number of freeze/thaw cycles. The presence of phases with different mobilities was observed using 13 C CP/MAS and DP/MAS NMR experiments. The degree of crystallinity of the a-PVA-rich phase was determined by ...
The behaviour of antiplasticized epoxy–amine networks was investigated by variable-temperature determinations of 1H NMR free induction decays. Up to 50°C, all antiplasticized resins exhibited a solid-like behaviour. At higher temperatures, resins containing the less polar additives were shown to be phase-separated, in contrast to systems containing polar additives. The temperature dependence of the...
1H nuclear magnetic resonance (n.m.r.) relaxation data, determined via either wide-line 1 H n.m.r. or high-resolution solid-state 13 C n.m.r., were used to analyse the existence and extent of interphasic regions in (methylmethacrylate)-b-(n-butylacrylate) block copolymers. Results thus obtained have shown that the as-obtained copolymers are not at thermodynamic equilibrium. ...
The local motions of an aromatic copolyester made from hydroquinone, hydroxybenzoic acid and isophthalic acid were investigated in trifluoroacetic acid/dichloromethane solution using 13 C n.m.r. The interpretation of the 13 C spin-lattice relaxation times was based on results previously obtained on aryl-aliphatic copolyesters obtained from ethylene glycol and hydroxybenzoic...
1H n.m.r. relaxation data, determined via either wide-line 1 H n.m.r. or high-resolution solid-state 13 C n.m.r., were used to analyse the existence and extent of interphasic regions in dimethylsiloxane-styrene block copolymers. Results thus obtained have shown that copolymers having very short blocks possess relatively large interphases characterized by intermediate mobility...
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