Search results for "Copolymer"
showing 10 items of 1003 documents
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.
Polysiloxane-backbone block copolymers in a one-pot synthesis: a silicone platform for facile functionalization.
2012
Block copolymers consisting exclusively of a silicon-oxygen backbone are synthesized by sequential anionic ring-opening polymerization of different cyclic siloxane monomers. After formation of a poly(dimethylsiloxane) (PDMS) block by butyllithium-initiated polymerization of D3, a functional second block is generated by subsequent addition of tetramethyl tetravinyl cyclotetrasiloxane (D4(V) ), resulting in diblock copolymers comprised a simple PDMS block and a functional poly(methylvinylsiloxane) (PMVS) block. Polymers of varying block length ratios were obtained and characterized. The vinyl groups of the second block can be easily modified with a variety of side chains using hydrosilylation…
The effect of macromolecular architecture of ethylene copolymers with multi-alkenylsilsesquioxane on morphological, rheological and dynamic mechanica…
2021
Abstract The influence of the degree and the way of incorporation of multi-alkenylsilsesquioxane into the polymer chain on morphological, rheological and dynamic mechanical parameters were determined. It was found that POSS incorporated into the polymer chain was located outside the crystalline structure of lamella in amorphous phase. The incorporation of POSS-6-2 as a pendant group resulted in significant increase of separation of macromolecules. The key factor in rheological and dynamic mechanical behavior of copolymers turned out to be the way of POSS incorporation into the polymer chain. The incorporation of POSS into the polymer chain as a pendant group resulted in decreased relaxation…
Some linear and branched macromolecules by ring-opening polymerization
1993
In the first part the ring-opening polymerization of some macrocyclic ether-acetals is briefly described. Of special interest are acetal polymers with functional groups, for instance C=C-double bonds. Appropriate unsaturated monomers and their polymerizability are discussed. The second part deals with the polymerization of oxazolines, substituted in 2- and/or 4-position. Branched polymers are obtained by copolymerization of 2-ethyl-2-oxazoline with 2-hexyl-2-oxazoline or 2-undecyl-2-oxazoline. The properties of the random copolymers and corresponding block copolymers are compared. By a “mixed mechanism technique” a block copolymer composed of a poly(tert -butyl methacrylate) block and a pol…
Effect of random copolymer additives on the interfacial tension between incompatible polymers
1998
Interfacial tensions γ were measured for mixtures of poly(methylphenylsiloxane) (4 kg/mol) and poly(dimethylsiloxane) (24 kg/mol) in the absence and in the presence of small amounts of the random copolymer poly(dimethylsiloxane-ran-methylphenylsiloxane) (89 mol-% of dimethylsiloxane units, 28 kg/mol) from 25 to 110°C. Approximately 1 wt.-% of the copolymer additive suffices to reduce γ from ca. 2.2 to 1.6 mN/m. The time dependence of the apparent γ value in the course of the attainment of equilibria also indicates surface acivity. The hypothesis is formulated that the efficiency of the random copolymer for a reduction of γ is bound to the condition that it is only sparingly soluble in both …
Polydispersity and Molecular Weight Distribution of Hyperbranched Graft Copolymers via “Hypergrafting” of ABm Monomers from Polydisperse Macroinitiat…
2013
The hypergrafting strategy designates the synthesis of hyperbranched graft copolymers (HGCs) in a grafting-from approach, using ABm monomers, from multifunctional, polydisperse macroinitiator cores by slow monomer addition. Hypergrafting leads to complex polymer topologies with defined molecular weight, degree of branching (DB), and polydispersity (PD). By a generating function formalism, a generally applicable equation for the PD of HGCs (PD = PDf + (m – 1)/f) is derived, where PDf is the polydispersity of the core and f its average functionality. In addition, the complete molecular weight distribution function has been calculated for varied m and f as well as for a given distribution of i…
Block Copolymers Build-up of Electron and Hole Transport Materials
2004
In this article we describe the synthesis of various monomers modified with triphenyl-1,3,5-triazine side groups as electron transport moieties. By nitroxide-mediated polymerization with a TEMPO unimer it was possible to obtain polymers with a narrow polydispersity. Furthermore, by living radical polymerization block copolymers were obtained from these monomers. Therefore, microphase separated structures are accessible which possess hole conducting moieties in one phase and electron conducting moieties in the other phase.
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…
Correlation between polymer architecture, mesoscale structure and photovoltaic performance in side-chain-modified poly(p-arylene-ethynylene)-alt-poly…
2011
Abstract Recent investigations have shown that an anthracene containing poly( p -arylene-ethynylene)-alt-poly( p -arylene-vinylene) statistical copolymer consisting of a well defined conjugated backbone, along which linear and branched alkoxy side chains are attached in a random manner, yields, compared to its counterparts with regular side chain substitution, an improved performance in polymer [6,6]:-phenyl-C 61 -butyric acid methyl ester (PCBM) bulk-heterojunction solar cells. The microscopic origin for the improved power conversion efficiency ( η ≈ 3.8%) of the statistical copolymer – which is the best in its material class – has not been resolved. We conducted grazing incidence wide-an…
Linear–dendritic block copolymers: The state of the art and exciting perspectives
2011
Concurrent with the rapid development of both dendrimers and hyperbranched polymers, a novel class of block copolymer architectures has emerged from the combination of these dendritic architectures with linear chains, the “linear–dendritic block copolymers” (LDBCs). This review gives a comprehensive summary of the state of the art in this rapidly developing field from pioneering early work to promising recent approaches.The different strategies leading to these hybrid architectures with either perfect dendrimer/dendron building blocks or imperfect, yet more conveniently accessible hyperbranched segments, are reviewed and compared. The consequences of the unusual polymer topology for supramo…