Guy Meyer

Kinetics of formation of polyurethane-poly(methyl methacrylate) interpenetrating polymer networks: 2. Synthesis of the rigid network in the presence of the elastomeric network

Abstract The kinetic aspects of the formation of a second network in the presence of the first have been studied in polyurethane-poly(methyl methacrylate) interpenetrating networks. The effect on kinetics of parameters such as the polyurethane content, the amount of acrylic crosslinker and the reaction temperature has been examined. It was found that the elastomeric polyurethane acts as a diluent that allows complete conversion of the acrylic monomers, and, through its viscosity, induces gelation of the reaction medium at the very beginning of the polymerization.

Polydimethylsiloxane/poly(methyl methacrylate) interpenetrating polymer networks: 2. Synthesis and properties

Abstract The synthesis of full and graft interpenetrating polymer networks (IPNs) based on polydimethylsiloxane and poly(methyl methacrylate) is described. IPNs were obtained by an in-situ sequential synthesis. Most samples were opaque; however, in a few cases, transparency was noted. Other properties like stress-strain behaviour, hardness and glass transition temperature were examined. Owing to the particular behaviour of silicone-containing polymers, the surface properties and the permeability to oxygen of these IPNs were also studied.

Kinetics of formation of polyurethane-poly(methyl methacrylate) interpenetrating polymer networks by Fourier transform infra-red spectroscopy: 1. Preliminary investigations

Abstract Fourier transform infra-red spectroscopy ( FT i.r.) was used to follow the kinetics of formation of polyurethane-poly(methyl methacrylate) interpenetrating polymer networks (PUR/PAc IPNs). In this study, the validity of the Beer-Lambert law for the present system was checked, and its limits determined. The synthesis of the individual networks, PUR and PAc, was studied by measuring the decrease of a characteristic absorption peak of each system. A first brief example of the application of this method to a PUR/PAc IPN is given.

Polydimethylsiloxane/poly(methylmethacrylate) interpenetrating polymer networks: 1. Efficiency of stannous octoate as catalyst in the formation of polydimethylsiloxane networks in methyl methacrylate

Abstract Deactivation of the polycondensation catalyst in in situ sequential syntheses of polydimethylsiloxane/poly(methyl methacrylate) interpenetrating polymer networks was observed, which impeded the gelation of the elastomeric network. The loss of catalytic activity could be ascribed to the simultaneous presence of radicals and oxygen in the reaction medium. When either oxygen is excluded or a radical inhibitor added, the polycondensation proceeds to gelation at the expected rate.

Competition between polycondensation of α,ω-dihydroxy polydimethylsiloxane and its condensation with alkoxy silane: A kinetic approach

Abstract α,ω-Dihydroxy polydimethylsiloxane (PDMS) undergoes a linear polycondensation, catalysed by stannous octoate, which can yield high molecular weight species. In the presence of monoalkoxysilane, both a polycondensation and a blocking reaction take place simultaneously. Such a condensation between α,ω-difunctional PDMS chains may also occur in the case of crosslinking involving tri- or tetra- alkoxysilane. This implies that, in the so-called model networks thus formed, the average length of the elastic chains is definitely different from that of the precursor chains.

Nuclear magnetic resonance lineshape studies of interpenetrating polymer networks

Abstract In the so-called in situ sequential interpenetrating polymer networks (IPNs), the two networks are formed after each other, and the network formed first is thought to impede gross phase separation in the final material. This is contrary to the other type of IPNs ( in situ simultaneous), in which the formation of both networks is initiated at once and proceeds to completion more or less simultaneously. In order to verify more accurately this assumption, which is not inconsistent with transmission electron microscopy findings, a solid-state nuclear magnetic resonance lineshape analysis technique has been used to investigate the degree of phase dispersion of IPNs of both types composed of an elastomeric polyurethane (PUR) (25 wt%) and a crosslinked poly(methyl methacrylate). The results confirm that such IPNs, when prepared sequentially, have a higher degree of phase dispersion than those obtained by the simultaneous synthesis method. Furthermore, in the corresponding neat PUR networks, built up from aromatic pluriisocyanate and poly(oxypropylene glycol) (POPG), the rigid crosslink points are not composed of isocyanate only, but include some oxypropylene mers; it appears that the amount of the rigidified part is the same, whatever the molecular weight of POPG.

Morphologies of semi and full interpenetrating polymer networks by nuclear magnetic resonance relaxation times

Full and semi interpenetrating polymer networks, IPNs, formed with a network of polyurethane (PU), and either a crosslinked poly(methyl methacrylate), PAc, or a linear polystyrene, PS, were synthesized with the aim of obtaining homogeneous materials. As already shown in a previous paper, the degree of phase dispersion in such materials depends on the synthesis method. The purpose of the n.m.r. investigations is to estimate the degree of mixing of the polymer in such networks, together with the synthesis parameters. The n.m.r. lineshape evolution of the PU/PAc IPNs with temperature allowed us to conclude that the PAc and PU networks are more intimately mixed in the sequential mode. In this paper, the measurements of the spin-lattice relaxation times in the rotating frame and the Goldman—Shen experiment are used to confirm previous results, and to give an estimation of the degree of mixing of the two networks in the matrix and of the size of the inclusions of PS in the simultaneous IPN. Following the same protocol, different semi-1 IPNs of PU/PS are examined in order to relate the amount of PS added to the reaction medium with the degree of advancement of the phase separation. Nodules of pure PS are seen for some samples but they do not correspond to those observed by SEM.

Linear polycondensation of α,ω-dihydroxy polydimethylsiloxane, catalyzed by stannous octoate

Abstract In the presence of stannous octoate, high molecular weight polydimethylsiloxane (PDMS) is obtained from an oligomeric α,ω-dihydroxy PDMS. The polycondensation reaction is limited by the presence of oxygen and/or water. Only linear species are found, and network formation has never been observed.

Morphology development during the polymerization of styrene within a polyurethane network: Investigations by small‐angle X‐ray and light scattering

Phase separation that takes place during the formation of semi-interpenetrating polymer networks based on crosslinked polyurethane and linear polystyrene was studied by small-angle X-ray scattering and light scattering. The kinetics of the chemical reactions was followed by Fourier transform infrared spectroscopy. The occurrence of broad peaks in the X-ray scattering curves was interpreted in terms of distances between the urethane crosslinks. Small modulations on these curves were assigned to sphere-like structures with a diameter of around 5 nm which might be related to the urethane crosslink regions. Small modulations on the light-scattering curves at the beginning of styrene polymerization were assigned to spheres with diameters of around 4.5 μm, which can be related to the polystyrene-rich phase. These modulations disappear with time, which might indicate an increasing polydispersity of the domain sizes. The final morphology was found to depend on the time at which polymerization of styrene is initiated with respect to the time of gelation of polyurethane.