Search results for "grafting"
showing 10 items of 201 documents
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…
Synthesis of Processable Inorganic‐Organic Hybrid Polymers Based on Poly(silsesquioxanes): Grafting from Polymerization Using ATRP
2008
Inorganic-organic hybrid polymers have been synthesized utilizing atom transfer radical polymerization (ATRP) from a functionalized poly(methylsilsesquioxane) (PMSSQ) macroinitiator. Different polymeric ATRP initiators were prepared by co-condensation of functionalized trichlorosilanes with methyltrimethoxysilane. Various vinyl monomers have been successfully grafted from these macroinitiators, demonstrating a highly variable synthetic concept, which offers the chance to synthesize a wide spectrum of inorganic-organic hybrid polymers. All synthesized polymers were soluble in various organic solvents. Spin-coating these hybrid materials onto various substrates could produce stable and adhere…
Design, Synthesis, and Use of Y-Shaped ATRP/NMP Surface Tethered Initiator.
2015
Heterogeneous polymer brushes on surfaces can be easily formed from a binary initiator on a silicon oxide substrate where two different types of polymers can be grown side-by-side. Herein, we designed a new Y-shaped binary initiator using straightforward chemistry for “grafting from” polymer brushes. This initiator synthesis takes advantage of the Passerini reaction, a multicomponent reaction combining two initiator sites and one surface linking site. This Y-shaped binary initiator can be synthesized in three steps with a higher yield than other similar initiators reported in the literature, and can be performed on a multigram scale. We were able to attach the initiator to a silicon oxide s…
Controlled Synthesis of Linear Polymers with Highly Branched Side Chains by “Hypergrafting”: Poly(4-hydroxy styrene)-graft-hyperbranched Polyglycerol
2012
Linear polymers with hyperbranched side chains are unusual macromolecular structures due to their high number of functional groups in the side chains as well as their potential cylindrical conformation in bulk or solution. In a three-step synthesis combining anionic and oxy-anionic polymerization, hyperbranched polyglycerol was “hypergrafted” from linear poly(4-hydroxy styrene) macroinitiators to yield poly(4-hydroxy styrene)-graft-hyperbranched polyglycerol. Successful grafting with control over molecular weight (10–31 kg·mol–1) and low PDIs (<1.4) was shown by various characterization techniques. All polymers have a high side chain density, due to rapid transfer of the initiating function…
Influence of Hair Density and Hair Length on Interparticle Interactions of Spherical Polymer Brushes in a Homopolymer Matrix
2003
The dynamics of hairy spherical nanoparticles in a melt of linear polymer chains has been investigated by mechanical spectroscopy as a function of particle topology and concentration. Using a simple free volume approach for the data analysis of the structural relaxation time vs concentration and the well-known hard-sphere result as a reference, a semiquantitative measure for the interparticle interactions, that is particle deformability/softness, and the effective particle size compared to the size of a nonswollen spherical brush has been determined. For these studies, model particles of hairy nanoparticles differing in either hair length or grafting density have been prepared. In contrast …
Synthesis of polyvinyl acetate-graft-poly-2-oxazolines
1994
Poly(vinyl acetate-co-vinyl chloroformate) (1) was synthesized via phosgenation of poly(vinyl acetate-co-vinyl alcohol). It was shown that (1) is capable of initiating the polymerization of 2-phenyl-2-oxazoline and 2-methyl-2-oxazoline, when the counter ion is exchanged using potassium iodide. Polyvinyl acetate-graft-poly-2-phenyl-2-oxazoline and polyvinyl acetate-graft-poly-2-methyl-2-oxazoline are obtained in the grafting reaction.
Fluidizing efficiency of comb-like superplasticizers: The effect of the anionic function, the side chain length and the grafting degree
2015
Superplasticizers and especially polycarboxylate grafted polyethylene oxide (PCE) demonstrated their efficiency to fluidify concrete. The aim of this work is to investigate the evolution of the fluidity as a function of adsorption in a sulfated solution with a wide variety of comb-like superplasticizers and at incomplete adsorption rate. Polymers with various side chain lengths, grafting ratios and also with modified anionic functions (carboxylate, dicarboxylate and phosphate) were synthesized. Inert calcite suspensions were used to mimic early age cementitious materials avoiding the cement hydration. Models of polymer conformation and yield stress prediction have been tested. But the most …
Functionalized halloysite multivalent glycocluster as a new drug delivery system.
2020
A new design for halloysite nanotube materials was obtained by grafting chemically modified cyclodextrin units onto the nanotube surface. In particular, grafted cyclodextrins were decorated with thiosaccharide pendants, in order to mimic the well-known binding of sugars to proteins and the glyco-cluster effect occurring during cellular recognition events. The obtained materials were characterized by using a combination of varied techniques (FT-IR spectroscopy, thermogravimetric analysis, scanning electron microscopy, dynamic light scattering, turbidimetry), and their potential drug-delivery abilities were tested by studying their interactions with the common naturally occurring anticancer a…
Surface coatings based on polysilsesquioxanes: Grafting-from approach starting from organic polymers
2009
AbstractPoly(methylsilsesquioxane) (PMSSQ) based hybrid materials are promising candidates to produce substrate-independent stable and adherent surface coatings. Usually these materials are synthesized by controlled radical polymerization from inorganic precursors. The presented synthetic pathway in here demonstrates how to graft PMSSQ networks from an endgroup-functionalized organic polymer and thus enlarges the range of accessible inorganic/organic hybrid coating materials.
High-energy radiation processing, a smart approach to obtain PVP-graft-AA nanogels
2014
Abstract Poly(N-vinylpyrrolidone)-grafted-acrylic acid biocompatible nanogels (NGs) were prepared using an exiting industrial-type electron accelerator and setups, starting from semi-dilute aqueous solutions of a commercial PVP and the acrylic acid monomer. As a result, NGs with tunable size and structure can be obtained quantitatively. Sterility was also imparted at the integrated dose absorbed. The chemical structure of the NGs produced was confirmed through Fourier Transformer Infrared Spectroscopy (FT-IR). The molecular and physico-chemical properties of NGs, such as the hydrodynamic dimensions and surface charge densities, for various polymer and monomer concentrations in the irradiate…