Search results for "polymerization"
showing 10 items of 1689 documents
Liquid crystalline phases from polymer functionalised semiconducting nanorods
2008
The orientation of semiconducting nanomaterials is a hot topic in optoelectronic applications. Liquid crystallinity offers the potential to orient inorganic anisotropic nanorods, if they can be solubilised sufficiently as realised by polymer functionalisation. In this work we functionalised TiO2, SnO2, ZnO and CdTe nanorods with PMMA, PS and PDEGMEMA (poly(diethylene glycol monomethyl ether) methacrylate) diblock copolymers containing anchor groupsvia grafting-to. The block copolymers were synthesised by RAFT polymerisation (PDI ≈ 1.2) via reactive ester diblock copolymers, which were functionalised later with anchor units polymer-analogously. The surface coverage of the nanorods (determine…
Molecularly imprinted composite materials via iniferter-modified supports
2002
Wide pore silica (DP = 100 nm) and gel-type or macroporous (12% nominal crosslinking density) Merrifield resins were modified with iniferter groups for grafting of crosslinked molecularly imprinted or non-imprinted polymer layers through quasi-living polymerisation. Prior to iniferter coupling, the silica supports were premodified by silanisation with p-(chloromethyl)phenyl trimethoxysilane. The iniferter groups were then introduced by reacting the resin-bound chloromethyl groups with sodium N,N-diethyldithiocarbamate. It was shown that the coupling yield, measured as the conversion of the chloromethyl groups, could be varied between 5 and 85% through kinetic control, with the fastest conve…
Modification of Polymer-Magnetic Nanoparticles by Luminescent and Conducting Substances
2014
The polymer encapsulated magnetic nanoparticles were obtained by suspension polymerization of styrene in the aqueous dispersion of magnetite. Functionalization of capsules was carried out by adsorp...
Structure of Polymer-Grafted Nanoparticle Melts.
2020
The structure of neat melts of polymer-grafted nanoparticles (GNPs) is studied via coarse-grained molecular dynamics simulations. We systematically vary the degree of polymerization and grafting density at fixed nanoparticle (NP) radius and study in detail the shape and size of the GNP coronas. For sufficiently high grafting density, chain sections close to the NP core are extended and form a dry layer. Further away from the NP, there is an interpenetration layer, where the polymer coronas of neighboring GNPs overlap and the chain sections have almost unperturbed conformations. To better understand this partitioning, we develop a two-layer model, representing the grafted polymer around an N…
The role of dislocations in the solid-state polymerization of monomers having conjugated triple bonds: A study of 2,4-hexadiyne-1,6-diol bis(p-toluen…
1975
The crystal structure of the monomer bis(p-toluene sulfonate) ester of 2,4-hexadiyne-1,6-diol (pT) is conducive from the viewpoint of both the separation distances and molecular configuration, to polymerization, irrespective of whether initiation is thermal, photochemical, or mechanical. The dislocations present in the monomer and polymer structures have been characterized by employing optical microscopic techniques. The slip system (102)[010] is found to be present in both monomer and polymer crystals but the (010)[001] system is found only in the monomer. On this basis a crystal structure for the monomer is proposed based on existing crystallographic information relating to the structure …
Cylindrical Polymer Brushes with Elastin-Like Polypeptide Side Chains
2013
Monodisperse high molar mass elastin-like polypeptide macromonomers comprising 20 pentasequences (M = 8332 g/mol) were radically polymerized to high degrees of polymerization Pw = 590. Polymerization was conducted in water well above the lower phase transition temperature, i.e., in the phase separated regime. The resulting polymers adopt a cylindrical shape as demonstrated by AFM pictures of solutions spin-cast on mica. The directional persistence of the cylindrical brushes was determined by static light scattering to Kuhn statistical segments lengths lk = 120 nm at 5 mM aqueous NaCl solution which decreased to lk = 54 nm at 0.65 M NaCl. Upon polymerization the phase transition temperature …
The Crystalline State of Macromolecular Substances
1974
Unlike low molecular weight substances, high polymers do not crystallize completely. However long the crystallization process is continued, they still consist of a mixture of crystalline and non crystalline regions. In the undrawn material, these regions form larger units which are known as spherulites. Questions that are of special interest concern the arrangement of the chains in the noncrystalline regions, the causes of chain folding, and the imperfections in the crystals. The incomplete crystallization is a consequence of kinetic inhibitions. This can be deduced from the fact that the crystalline fraction increases with rising crystallization temperature. If polymerization is carried ou…
Polydithienothiophenes: Two new conjugated materials with narrow band gap
1997
Abstract The electrochemical polymerisation of dithieno[3,4-b:3',2'-d]thiophene and dithieno[3,4-b:2',3'-d]thiophene leads to conjugated materials with narrow band gap in which the p- and n-doping processes are possible in organic electrolytes. The spectroelectrochemical study of these polymers is reported.
X-ray topographic study of solid-state polymerized poly-[1,2-bis-(p tolylsulphonyloxymethylene)-1-butene-3-inylene]
1976
Local extinction contrast effects have been observed in macroscopic polymer crystals, using Berg-Barrett X-ray topography. Results from as-polymerized crystals indicate that the crystals are perfect enough for defect regions to be imaged. As-polymerized crystals exhibited apparent defects lying along [021]. [010] slip traces in the (100) surface of a crystal were imaged; the slip system here appears to be consistent with (h01) [¯10h], forh, l ≠ 0 and [010] the chain direction.