NMR study of water bound to soft segments in thermoplastic elastomers

The interaction between water absorbed in four hard-soft segment block-copolymers and the polymer chains is investigated by pulsed field gradient echo NMR spectroscopy and Nuclear Overhauser NMR spectroscopy. The results show, depending on the structure and mass fraction of the soft segments, a strong interaction between water and the soft segments. Most likely this is due to a hydrogen bond between water and the ether groups. The self-diffusion of water has been determined and is described as a jumping process between the ether sites with a residence time t and a time between sites t. It is found that the residence time is of the order of a few ns and also that the ratio t/τ decreases with increasing soft segment rigidity.     

Towards photonic ink (P-ink): a polychrome,fast response metallopolymer gel photonic crystal device

We demonstrate here a new kind of planarized and oriented colloidal photonic crystal device whose optical stop-band position, width and intensity can be reversibly redox and solvent tuned over a broad wavelength range by an anisotropic expansion of the photonic lattice. The material is composed of silica microspheres in a matrix of crosslinked polyferrocenylsilane^[1], a metallopolymer network with a continuously variable state of oxidation^[2]. Optical data was fitted using a scalar wave approximation, with a congruence to experimental data, allowing facile extraction of information concerning polymer swelling behaviour. The chemomechanical polychrome optical response of the material was exceptionally fast, attaining its fully swollen state from the dry shrunken state on a sub-second time-scale.     

Relationship between swelling and mechanical properties of cross-linked polymers mixed with sand

Cross-linked polymers consisting of acrylamide, sodium acrylate, starch fragments and a cross-linker were synthesized with the same content of carboxyl groups and three degrees of cross-linking Q of 0.04, 0.2 and 1 wt%. An increase in Q gradually reduces the swelling of polymer gels in water; when distributed in sand, polymer gels exhibit maximum swelling at Q = 0.2 wt%. It is shown that the behavior of polymer gels in sand is determined by the balance between the elasticity of swollen polymer gels and the resistance of sand particles     

Shrinking Behavior of Surfactant‐Grafted Thermosensitive Gels and the Mechanism of Rapid Shrinking

Surfactant‐grafted hydrogels with a fast response to temperature were prepared. In order to clarify the mechanism of rapid shrinking, the effects of the grafted surfactant and the homogeneity of the main chain were investigated. Poly(NIPAAm‐co‐S180A) gels prepared using a chemical cross‐linker (bis‐PNS gels) exhibited rapid shrinking, as did PNS gels prepared by γ‐ray irradiation (γ‐PNS gels). This suggested that the rapid shrinking of the PNS gel did not depend on the homogeneity of the main‐chain structure. The shrinking kinetics of the bis‐PNS gels depended on the amount of the introduced surfactant, which means that shrinking is enhanced by micelle formation as a dynamic driving force. From the analysis by dynamic light scattering (DLS) and scanning microscopic light scattering (SMILS), it was suggested that the micelle structure, which induced rapid shrinking, existed in the bis‐PNS gel.

     

Application of sensitive hydrogels in chemical and pH sensors

In the present work, pH-sensitive poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blends as well as hydrogels based on poly(N-isopropylacrylamide) (PNIPAAm), which are sensitive to organic solvent concentration in aqueous solutions, were used in silicon micromachined sensors. A sensitivity of approximately 15 mV/pH was obtained for a pH sensor with a 50 μm thick PVA/PAA hydrogel layer in a pH range above the acid exponent of acrylic acid (pK_a=4.7). The output voltage versus pH-value characteristics and the long-term signal stability of hydrogel-based sensors were investigated and the measurement conditions necessary for high signal reproducibility were determined. The influence of the preparation conditions of the hydrogel films on the sensitivity and response time of the chemical and pH sensors is discussed.     

Multi-Layer Pipes for Hydrocarbons Conveyance

The replacement of metals with plastics in piping systems is a well established practice in a vast range of public and industrial applications. However, difficulties still exist, mainly related to the limited chemical resistance of the polymers commonly used in pipe manufacturing to some conveyed fluids. This prevents using plastic pipes in important applications such as the transport of liquid hydrocarbons, particularly in oil fields. The use of chemically resistant polymers, such as fluorinated polyolefins, is precluded by high cost and poor mechanical properties. Co-extrusion of multi-layer pipes carrying an internal chemically resistant liner can be a viable alternative capable to extend the use of plastic pipes to refining and chemical industries. An experimental PE/PA multi-layer pipe has been developed whose resistance to diffusion and mechanical properties have been tested. Tests in real oil fields confirm the good performance of the new pipes.