Search results for "Polymers"
showing 10 items of 3567 documents
Self-organization of hydrophobized polyzwitterions
1992
Abstract Several series of copolymers of different geometry were synthesized from zwitterionic surfactant monomers and polar non-ionic comonomers. Bulk properties were investigated by d.s.c. and X-ray scattering. The copolymers were amorphous, but exhibited superstructures up to high commonomer contents. Solubility of the copolymers was determined as a function of geometry and composition. From the results, a main chain spacer model has been derived. All water-soluble copolymers exhibited characteristic features of classical polysoaps, as shown by surface tension measurements and by solubilization of pyrene. But gradual differences depending on the polymer geometry were observed for the sol…
Micelles Formed by Cylindrical Brush-Coil Block Copolymers
2005
Amphiphilic cylindrical brush-coil block copolymers consisting of a polystyrene coil and a cylindrical brush block with poly(acrylic acid) side chains are prepared by ATRP of t-butylacrylate from a block comacroinitiator. Upon acidolysis of the poly(t-butylacrylate), water-soluble polymers were obtained that were observed to form micelles consisting of 4-5 block copolymers on average in aqueous solution. The star-like nature of such micelles was clearly visualized by scanning force microscopy.
Nanoscale mechanical characterization of polymers by AFM nanoindentations: Critical approach to the elastic characterization
2006
AFM nanoindentations show a dependence of penetration, i.e., the relative motion between the sample and the tip (indenter), on material elastic properties when using the same load. This elationship becomes visible by using of samples being homogeneous down to the scale of nanoindentation. They were prepared from materials covering a broad range of mechanical behavior: from rubbery networks to glassy and semicrystalline polymers. The elastic modulus can be obtained applying Sneddon’s elastic contact mechanics approach. To do this, some calibrations and instrumental features have to be measured accurately. All the polymers tested show that the contact between the tip and the sample is dominat…
A “click” approach to ROMP block copolymers
2008
Amphiphilic block copolymers can be conveniently prepared via convergent syntheses, allowing each individual polymer block to be prepared via the polymerization technique that gives the best architectural control. The convergent “click-chemistry” route presented here, gives access to amphiphilic diblock copolymers prepared from a ring opening metathesis polymer and polyethylene glycol. Because of the high functional group tolerance of ruthenium carbene initiators, highly functional ring opening metathesis polymerization (ROMP) polymer blocks can be prepared. The described synthetic route allows the conjugation of these polymer blocks with other end-functional polymers to give well-defined a…
Liquid Crystals from Polymer-Functionalized TiO2 Nanorod Mesogens
2008
In this work, we functionalized TiO2 nanorods with dopamine-functionalized diblock copolymers. After functionalization, they are well dispersible in organic solvents. Light scattering proves that t...
Novel Amphiphilic Styrene-Based Block Copolymers for Induced Surface Reconstruction
2008
This paper describes the synthesis of amphiphilic block copolymers by living radical polymerization (NMP) of new styrene-like monomers. The polar monomers (ethylene oxide side chains and free hydroxyl- or amino-groups after deprotection) were polymerized in a “protected form” to adjust the solubility of the monomers. In this way high molar mass polymers with a narrow polydispersity (around or below 1.2) were accessible. In the bulk state hydrophobic and hydrophilic domains demix. By exposing thin films of these polymers to vacuum (air) or alternatively to water or a hydrophilic surface it becomes possible to switch the surface polarity reversibly between contact angles of about 105° and 83°…
Copolymerization of methacryloyl-terminated PMMA macromonomers with methyl methacrylate
1992
Methacryloyl-terminated macromonomers (MM) of polymethylmethacrylate (PMMA) of two different molecular weights were prepared by group transfer polymerization (GTP). They were copolymerized with methyl methacrylate (MMA) by radical polymerization using toluene as the solvent. The relative reactivity of the MM, 1/r1, decreases with increasing initial MM concentration. This is interpreted as a consequence of the increasing viscosity of the reaction medium leading to an increasing diffusion control of the MM addition. At a constant weight ratio of MMA to MM the reactivity of the longer macromonomer is higher than of the shorter one. Increasing the molar ratio [MMA]/[MM], i.e. increasing the ave…
Synthesis of well-defined polymeric activated esters
2008
Monomers bearing an activated ester group can be polymerized under various controlled polymerization techniques, such as ATRP, NMP, RAFT polymerization, or ROMP. Combining the functionalization of polymers via polymeric activated esters with these controlled polymerization techniques generate possibilities to realize highly functionalized polymer architectures. Within this highlight two different research areas of activated esters in polymer science will be discussed: (i) the preparation of defined reactive polymer architectures by controlled polymerization techniques and (ii) the preparation of defined reactive thin films. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6…
Synthesis of Functional Inorganic−Organic Hybrid Polymers Based on Poly(silsesquioxanes) and Their Thin Film Properties
2008
New stable and adherent coating materials have been synthesized on the basis of inorganic/organic hybrid polymers. As the inorganic part, different poly(silsesquioxanes) (PSSQ) have been functionalized to act as polymeric chain transfer agents (CTAs) for a reversible addition fragmentation chain transfer polymerization, thereby determining the starting point of a controlled radical polymerization of vinyl-type monomers. Using two different CTAs acrylates, we have successfully polymerized methacrylates and styrene under RAFT polymerization conditions. Different monomers were copolymerized in such an organic block to incorporate multiple functionalities. The variation of the block ratios and …
Mechanical relaxation in miscible polymer systems: the glass transition regime in poly(vinylmethylether) (PVME)-cross-polystyrene (PS) semi-interpene…
1990
Abstract Miscible semi-interpenetrating polymer networks (semi-IPN) of varying composition are prepared by crosslinking polystyrene containing few maleic anhydride groups with a diamine in the presence of linear poly(vinylmethylether) (PVME). The resulting PVME-c-P(ScoMA) semi-IPNs are characterized by their thermal and thermomechanical behaviour. Comparison with the corresponding uncrosslinked material proves that weak crosslinking has a negligible effect on the location of the glass transition as measured by d.s.c. Both the Tg data and the temperatures of the loss modulus maximum E″ (at 1 rad/s) show the same non-linear curved composition dependence. Contrary to this the tan δ maximum var…