Search results for "Polystyrene"
showing 10 items of 349 documents
The mechanism of polymer permeation through polymer gel membranes
2007
Polymer gels are capable of producing separation effects on polymers. Applications for fractionation and for osmotic measurements are possible. Investigations are reported concerning the separation properties of polystyrene layers grafted onto a supporting cellulose basis. The permeation for pure solvents and the separating molecular limit for different solvents are tested. Their size depends uniquely on the interaction between the grafted polystyrene and the solvent.
Blends from redox active liquid crystal ionomers and amorphous ionomers
1994
Abstract Biphasic blends (mixtures) of liquid crystal ionomers (prepared from ferrocene containing liquid crystal polymers by a redox reaction) and partially sulfonated polystyrene combine the constituent properties in a way, which is dependent on the measuring method. Polarizing microscopy shows homogenous textures similar to the pure liquid crystal polymer. Mechanical measurements show however the elastomeric behaviour of sulfonated polystyrene. The phase separated structure of these blends is proved by differential scanning calorimetry measurements.
Neutron reflectometry studies on the interfacial width between polystyrene and various poly(alkylmethacrylates)
1999
From neutron reflectometry we have obtained the interfacial width (typically 2-8 nm) between incompatible polymers above the glass transition temperatures. The investigated polymer bilayers consist of a deuterated polystyrene top layer and various poly(alkylmethacrylates) as a bottom layer. We obtained interesting effects of the length of the alkyl group on the interfacial width. Using mean-field theory we calculate Flory-Huggins-Stavermann interaction parameters X from the interfacial width a I data. These results are compared with investigations of the interfacial width between deuterated poly(methylmethacrylate) and respective polyalkyl-methacrylates.
One-Step Block Copolymer Synthesis versus Sequential Monomer Addition: A Fundamental Study Reveals That One Methyl Group Makes a Difference
2018
Block copolymers of polyisoprene and polystyrene are key materials for polymer nanostructures as well as for several commercially established thermoplastic elastomers. In a combined experimental and kinetic Monte Carlo simulation study, the direct (i.e., statistical) living anionic copolymerization of a mixture of isoprene (I) and 4-methylstyrene (4MS) in nonpolar media was investigated on a fundamental level. In situ 1H NMR spectroscopy enabled to directly monitor gradient formation during the copolymerization and to determine the nature of the gradient. In addition, a precise comparison with the established copolymerization of isoprene and styrene (I/S) was possible. Statistical copolymer…
Diffusion of spherical micronetworks in polymer diluent systems and melts studied by dynamic light scattering techniques
1994
Spherical polystyrene (PS) micronetworks can be prepared in microemulsion with bulk radii of 5–60 nm and different cross-linking densities. The diffusion of these PS spheres has been studied in polymer diluent systems ranging from dilute solutions to plasticized melts by using forced Rayleigh scattering and photon correlation spectroscopy. On increasing the PS concentration, a colloid glass transition is observed at a volume fraction ΦC ≈ 0.64 of the swollen spheres. At higher concentration inside the “colloid glass” state the sphere diffusion is slowed down and becomes very complex but can be observed up to the limit of a melt of collapsed spheres.
Ferroelectric block copolymers
1997
A block copolymer consisting of polystyrene and a side chain ferroelectric liquid crystalline polymer was synthesized using polymer analogous chemistry on a monodisperse poly(styrene-b-isoprene). Composition was adjusted to give lamellar microstructure after addition of the mesogenic side groups. If placed in an LC cell without orientation of domains, no ferroelectric response was observed. After shearing the thin film, presumably due to alignment of lamellae, a bistable ferroelectric switching could be detected.
Polymer-polymer interaction parameters in solvent/polymer/polymer ternary systems
1981
Abstract Empirical equations defining the relationships between b23 and χ23 interaction parameters for the ternary systems toluene (1)/poly(dimethylsiloxane), PDMS, (2)/polystyrene, PS, (3) and benzene (1)/PDMS(2)/PS(3) have been determined. The dependences of both interaction parameters on the mean molecular weights of the macromolecular components have also been studied. A single dependence of b23 (or χ23) upon the mean molecular weight is found when both polymeric components have intermediate to high molecular weights. However, that single dependence is not found when the molecular size of polymer (2) is low.
Living Polymer Chains with Predictable Molecular Weight and Dispersity via Carbanionic Polymerization in Continuous Flow: Mixing Rate as a Key Parame…
2016
Aiming at systematic variation of the parameter dispersity, Đ (or “polydispersity”), living polymers with predictable dispersity (Đ = 1.15–2.20) and controlled molecular weights (Mn = 3200–18 500 g mol–1) were prepared via carbanionic polymerization. The approach relies on a continuous flow reactor equipped with a tangential four-way jet micromixing device. By varying the total flow rate, the mixing efficiency of the initiator (sec-BuLi) and the corresponding vinyl monomers is controlled, resulting in polymers with predefined dispersity, while the number-average molecular weight, Mn, is kept constant. In this manner living polystyrene (PS), poly(p-methylstyrene) (PpMeS), and poly(2-vinylpyr…
Nanoscale Blends between Immiscible Polymers via Simultaneous Non-Interfering Polymerisation
2005
An important topic in polymer science seeks to improve the performances of polymer blends using nanoscale phase segregation. Here, blends between polystyrene and polycaprolactone are realised by a chemical route. The non-interfering character of the radical polymerisation of styrene and the lanthanide halide initiated ring-opening polymerisation of caprolactone is assessed. The molecular weights range from 2 000 to 3 500 for polycaprolactone and up to 140 000 for polystyrene, with reasonable polydispersity indexes. From calorimetry measurements, it is shown that polystyrene and low molecular weight polycaprolactone are immiscible. The morphology of the blends between the two immiscible poly…
Functional Diblock Copolymers for the Integration of Triboluminescent Materials into Polymer Matrices
2008
This work describes the synthesis and use of new diblock copolymers to integrate functional inorganic particles into a polymer matrix. These diblock copolymers were synthesized by nitroxide-mediated polymerization (NMP) from styrene and two styrene-like monomers with protected functional groups for the later connection to the functional inorganic material. It was possible to keep the polydispersity of the block copolymers around or below 1.2 and to preset the length of the functional block to about 20 monomers or 10 mol-% of monomers. The groups for the surface functionalization (amino groups or chelating ligands) were obtained in their free form by polymer analogous reactions. As an exampl…