Search results for "rafting"

Microphase separation in bottlebrush polymers under poor-solvent conditions

2009

Molecular-dynamics simulations are used to study the structure of bottlebrush polymers with rigid backbones, for various grafting densities, side chain lengths, and varying solvent quality. While we confirm different states of the bottlebrush proposed by Sheiko et al. (Eur. Phys. J. E, 13 (2004) 125) we find that the transition between stretched and collapsed brushes occurs in a rather gradual manner. The pearl-necklace structure occurring at intermediate grafting densities and rather low temperatures has a pronounced medium-range order along the backbone.

Irradiation of low density and high density polyethylenes in presence of carbon dioxide in subcritical and supercritical conditions

1998

Abstract The grafting of carboxylated and oxygenated functions on low density and high density polyethylenes is carried out by gamma irradiation in the presence of carbon dioxide. Both crosslinking and grafting of oxidised groups occur. The extent of these molecular modifications depends on the physical conditions of the gas phase and on the nature of the polymer matrix.

Impact of surface state on polyethylene glycol conformation confined inside a nanopore.

2021

Solid-state nanopores are a promising platform for characterizing proteins. In order to improve their lifetime and prevent fouling, Polyethylene Glycol (PEG) grafting is one of the most efficient and low-cost solutions. Different models to calculate the PEG thickness do not consider their interaction with the nanopore inner surface nor the effect of confinement. Here, we investigate by molecular dynamic simulation the PEG conformation inside a nanopore in the case of hydrophobic and hydrophilic nanopores. Our results reveal that the nanopore inner surface plays a role in the PEG organization and, thus, in the speed of the salt constituent. The resulting pair interaction between PEG and its …

Biocompatible Poly(N-isopropylacrylamide)-halloysite Nanotubes for Thermoresponsive Curcumin Release

2015

The grafting of poly(N-isopropylacrylamide) (PNIPAAM) onto the halloysite external surface is proposed in order to obtain a novel thermoresponsive drug carrier for curcumin delivery. The new nanomaterial is characterized by means of FT-IR spectroscopy, thermogravimetric analysis, and SEM investigations. A high density of polymer chain was achieved at the nanoparticle surface. The PNIPAAM dehydration phenomenon was observed in water above 32 °C that is nearly coincident with the lower critical solution temperature for the polymer. The colloidal stability as well as the wettability of the obtained nanomaterial may be triggered by temperature stimuli. In vitro tests simulating the gastro-intes…

Grafting of Molecularly Imprinted Polymer Films on Silica Supports Containing Surface-Bound Free Radical Initiators

2001

Silica particles containing surface-bound free radical initiators have been used as supports for the grafting of thin films of molecularly imprinted polymers (MIPs). This technique offers a means of fine-tuning the layer thickness for improved kinetic properties or enhanced capacity in chromatographic or sensor applications. Thus prepared MIPs imprinted with l-phenylalanine anilide, have been characterized by FT-IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), elemental analysis, fluorescence microscopy, and scanning electron microscopy (SEM), providing evidence concerning the reproducibility in each step and the quantity and quality of the grafted…

1986

In order to graft methacrylonitrile onto preformed networks containing thermolabile azo groups, the monomer was used to swell the networks and then the temperature raised to the decomposition temperature for the azo groups. The unusually high grafting efficiencies yields (e) achieved are explained in terms of both the differences in the reactivities of the primary radicals formed and side reactions, which lead to additional grafting sites. As an aid to understand the dependence of monomer conversion on that of the initiator a kinetic model is discussed, which involves the consideration of the polymerization taking place both in the homogeneous phase and within the polymer pearls, which can …

Immobilisation of humic substances

2002

Attempts were made to immobilise humic substances (HS) by grafting them onto different carriers (styrene-divinylbenzene copolymers, cellulose and silica) as well as by their crosslinking with formaldehyde. Reaction with Merrifield resin was used for the immobilisation of HS, coupling by means of water-soluble carbodiimides to carriers containing amino-groups. Crosslinking of HS with formaldehyde (also in presence of other substances able to enter polycondensation reactions with formaldehyde) was shown to be an efficient method for their insolubilisation. Properties of the obtained immobilised HS were studied, including their potential use as sorbents for several metal ions and organic subst…

Modular Small Diameter Vascular Grafts with Bioactive Functionalities.

2015

We report the fabrication of a novel type of artificial small diameter blood vessels, termed biomimetic tissue-engineered blood vessels (bTEBV), with a modular composition. They are composed of a hydrogel scaffold consisting of two negatively charged natural polymers, alginate and a modified chitosan, N,O-carboxymethyl chitosan (N,O-CMC). Into this biologically inert scaffold two biofunctionally active biopolymers are embedded, inorganic polyphosphate (polyP) and silica, as well as gelatin which exposes the cell recognition signal, Arg-Gly-Asp (RGD). These materials can be hardened by exposure to Ca(2+) through formation of Ca(2+) bridges between the polyanions, alginate, N,O-CMC, and polyP…

Whose voice? Understanding stakeholder involvement in law drafting affecting Sami reindeer herding

2019

A communication and a legal approach are combined to investigate stakehold-er involvement in law drafting affecting Sami reindeer herding. The thesis fo-cuses on Finland, participation in law drafting in the Act on Metsähallitus (For-est Management and Park Services) and consultation related to the adoption of the International Labour Organization (ILO) Convention No. 169 concerning Indigenous and Tribal Peoples in Independent Countries. The research aims at gaining a better understanding of communication preceding and during law drafting processes regarding indigenous land use. It clarifies the changing con-text of the law drafting in which the issue of land use is addressed. Study 1 provi…

Gender Neutrality in Legislative Drafting Techniques. Where conventionality in English Language Meets Creativity in a Diachronic Perspective

2019

Over the last decades, proposals to modernise legislative drafting have been choral and among the specific causes generally mentioned there are sentences of undue length, overuse of archaic expressions, repeated definitions and expressions, partiality of nominalisations, lack of gender neutrality. The aim of this analysis is to explore the legislative techniques adopted by drafters of English-speaking countries over the last decades, who are asked to write legal sentences aiming at gender fair and symmetric representation of men and women. The issue examined from a lexico-grammatical perspective culminates in the proposed questions whether certain techniques used to implement gender-neutral…