The classical Doi‐Edwards model describes the dynamics of polymer strands between entanglements and predicts stress in linear polymers. This contribution considers the dynamics of whole molecules within the same tube picture. The probability distribution function of the end‐to‐end molecule vectors after deformation and retraction was calculated. The second moment of the distribution function coincides with that derived earlier by Doi and Edwards. The damping function shows considerably weaker thinning if the molecule end‐to‐end vector is considered as a Hookean spring. The present model describes one of the possible mechanisms leading to weaker damping exhibiting, e.g., by branched polymers.
Novel poly(ethylene glycol) (PEG) derivatives having both carboxylic acid, and sugar side chains were synthesized. These polymers were used to coat DNA/poly(ethyleneimine) complexes, and effectively protected them against albumin-induced aggregation. They presented carbohydrate moieties on the DNA complex surfaces as a cell-binding ligand, and the galactose-bearing polymer remarkably enhanced the poly(ethyleneimine)-mediated gene transfection on HepG2 cells.
Synthesis of poly(ethylene glycol) derivatives having both carboxylic acid and sugar pendant groups. 相似文献
A nickel α‐diimine catalyst was used for Grignard metathesis (GRIM) polymerization of 2,5‐dibromo 3‐hexylthiophene and 2‐bromo‐5‐iodo‐3‐hexylthiophene monomers. GRIM polymerization of 2‐bromo‐5‐iodo‐3‐hexylthiophene generated regioregular polymers with molecular weights ranging from 3 000 to 12 000 g · mol−1. The nickel α‐diimine catalyst was also successfully used for the GRIM polymerization of a bulky benzodithiophene monomer.
Surface modification of commercial PPBs with different saccharides is described. Surface‐glycosylated PPBs were prepared through reaction between the hydroxyl groups of poly(HEMA) and acetylated saccharides such as α‐glucose pentaacetate, β‐galactose pentaacetate, and lactose octaacetate. The modified PPBs were characterized by XPS and water contact angle measurement. It was found that the grafting degree of poly(HEMA) increases with UV irradiation time, monomer concentration, and water content in solvent. The binding degree of monosaccharides is higher than that of disaccharides. The glycosylated PPBs can selectively recognize lectins, indicating potential for protein isolation.
Reversible addition fragmentation chain transfer (RAFT) polymerization is one of the most extensively studied reversible deactivation radical polymerization methods for the production of well‐defined polymers. After polymerization, the RAFT agent end‐group can easily be converted into a thiol, opening manifold opportunities for thiol modification reactions. This review is focused both on the introduction of functional end‐groups using well‐established methods, such as thiol‐ene chemistry, as well as on creating bio‐cleavable disulfide linkages via disulfide exchange reactions. We demonstrate that thiol modification is a highly attractive and efficient chemistry for modifying RAFT polymers.
The establishment of advanced living/controlled polymerization protocols allows for engineering synthetic polymers in a precise fashion. Combining advanced living/controlled polymerization techniques with highly efficient coupling chemistries facilitates quantitative, modular, and orthogonal functionalization of synthetic polymer strands at their chain termini as well as side‐chain functionalization. The review highlights the current status of selected post‐functionalization techniques of polymers via orthogonal ligation chemistries, major characteristics of the specific transformation chemistry, as well as the characterization of the products.
Summary: The growth of surface‐initiated poly([2‐(methacryloyloxy)ethyl]trimethylammonium chloride) (pMETAC) brushes by ATRP was monitored by the quartz crystal microbalance technique with dissipation (QCM‐D). The change in mass of the quartz crystals starting from the adsorption of a thiol initiator monolayer through to the growth of the polymer brushes was determined. The use of QCM‐D allowed determination of the kinetics of polymerization from the surface. The technique can be applied to other polymers synthesised from surfaces and allows the study of varying conditions on the polymerization kinetics.
Changes in frequency of a quartz crystal during polymerization. 相似文献
The shielding effect of nano TiO2 on collagen under UV radiation was investigated using UV spectrophotometry. The results indicate that the shielding of collagen under UV radiation in the presence of nano TiO2 is significant. For 2.5 wt.‐% of TiO2, there is a greater shielding effect of UV radiation than that for 0.5 wt.‐% of TiO2. In addition, this study gives hints that a novel tanning agent with a UV shielding function can be formulated by using nano TiO2.
UV absorption of collagen under UV radiation after adding 2.5 wt.‐% TiO2. 相似文献
We describe an enzyme‐responsive polymeric vehicle, which is of great interest in controlled drug delivery, biosensing, and other related areas. The polymer synthesized using lipase as catalyst in DMSO has a favorable molecular structure that is quickly hydrolyzed by lipase in aqueous phase, and allows a fast release of encapsulated molecules.
This review covers the literature concerning the modification of polysaccharides through controlled radical polymerizations (NMP, ATRP and RAFT). The different routes to well‐defined polysaccharide‐based macromolecules (block and graft copolymers) and graft‐functionalized polysaccharide surfaces as well as the applications of these polysaccharide‐based hybrids are extensively discussed.
Poly[2‐(methacryloyloxy)ethyl phosphorylcholine] ‐modified gold surfaces, which have been newly prepared by a ‘grafting to’ method using a series of monosulfanyl‐terminated PMPC, are characterized by protein adsorption experiments based on surface plasmon resonance spectroscopy and ellipsometry measurements. The extent of BSA adsorption on PMPC‐modified surfaces was systematically reduced for thicker PMPC layers, thus the number of MPC units on the gold surface appears to be an important factor for the excellent protein resistance offered by PMPC‐modified gold surfaces fabricated by the ‘grafting to’ method, which is sharp contrast to that of PEG tethered chains.
