Search results for "Polymers."

Hydrophilic and Hydrophobic Polymeric Derivatives of Anti-Inflammatory Agents Such as Alclofenac, Ketoprofen, and Ibuprofen

1991

Macromolecular prodrugs of a hydrophilic polymer [α,β-poly( N- hydroxyethyl)-DL-aspartamide (PHEA)] was used as a drug carrier. Three poly- (HEA)-NSAID adducts were studied: poly(HEA)-Alclofenac, poly(HEA)-Keto profen, and poly(HEA)-Ibuprofen. Prodrugs with different drug content were synthesized both as water-soluble and water-insoluble agents. Hydrolysis of water-soluble adducts in a simulated gastric juice was studied.

Polymerization reactions and modifications of polymers by ionizing radiation

2020

International audience; Ionizing radiation has become the most effective way to modify natural and synthetic polymers through crosslinking, degradation, and graft polymerization. This review will include an in-depth analysis of radiation chemistry mechanisms and the kinetics of the radiation-induced C-centered free radical, anion, and cation polymerization, and grafting. It also presents sections on radiation modifications of synthetic and natural polymers. For decades, low linear energy transfer (LLET) ionizing radiation, such as gamma rays, X-rays, and up to 10 MeV electron beams, has been the primary tool to produce many products through polymerization reactions. Photons and electrons in…

What Limits the Molecular Weight and Controlled Synthesis of Poly(3-alkyltellurophene)s?

2016

Polytellurophenes are an emerging class of conjugated polymers; however, their controlled polymerization leading to high molecular weight materials has been a major challenge. Here we present a systematic investigation of the synthesis of poly(3-alkyltellurophene)s using the catalyst transfer polycondensation methodology. Learning that previous syntheses were limited by both polymerization reaction kinetics and polymer solubility, we design new tellurophene monomers to overcome these limitations. Controlled polymerization behavior up to Mn = 25 kDa, chain extension, block copolymerization, external initiation, and well-defined end groups are demonstrated for poly(3-alkyltellurophene)s with …

Branched and Functionalized Polybutadienes by a Facile Two-Step Synthesis

2008

Anionic polymerization was used to prepare silane-endfunctionalized polybutadiene macromonomers with different molecular weights ranging from 9 000 to 34000 g .mol- 1 . These were polymerized by a hydrosilylation reaction in bulk to obtain branched polymers, using Karstedt's catalyst. Surprisingly, the addition of monofunctional silanes during the polymerization showed only a minimal effect concerning the degree of polymerization. Furthermore, it was possible to introduce a variety of functional silanes without increasing the overall number of reaction steps by a convenient AB 2 + A type "pseudocopolymerization" method. All branched polymers were analyzed by SEC, SEC-MALLS, SEC-viscosimetry…

Kinetic Analysis of “Living” Polymerization Processes Exhibiting Slow Equilibria. 5. Effect of Monomer Transfer in Cationic Polymerization and Simila…

1996

This work deals with the kinetics of polymerization processes with chain transfer to monomer and reversible formation of dormant species. Such a mechanism is typical for cationic polymerization in the presence of Lewis acids as co-initiators. The expressions of number- and weight-average degrees of polymerization and polydispersity index are derived rigorously for a mechanism with free ions as the active species, but it is also applied to other mechanisms, e.g., ion pairs as active species. Plots of polydispersity index versus monomer conversion can be easily computed on a PC computer even though the expressions for the weight-average degree of polymerization and the concentration of residu…

Detection and visualization of physical knots in macromolecules

2010

Abstract This manuscript provides a pedagogical introduction on how to determine and visualize simple physical knots occurring in polymers, proteins and DNA. We explain how the Alexander polynomial is computed and implemented in a simulation code, and how the structure can be simplified beforehand to save computer time. The concept of knottedness can also be extended in a statistical framework to chains which are not closed. The latter is exemplified by comparing statistics of knots in open random walks and closed random loops.

Nanodevices based on a novel galactosaminated phospholipid-polyaspartamide for liver targeting of a ribavirin prodrug

2011

Organobase-Catalyzed Synthesis of Multiarm Star Polylactide With Hyperbranched Poly(ethylene glycol) as the Core

2011

Multiarm star copolymers consisting of the polyether-polyol hyperbranched poly(ethylene glycol) (hbPEG) as core and poly(L-lactide) (PLLA) arms are synthesized via the organobase- catalyzed ring-opening polymerization of lactide using hbPEG as a multifunctional macroinitiator. Star copolymers with high molecular weights up to 792 000 g mol−1 are prepared. Detailed 2D NMR analysis provides evidence for the attachment of the PLLA arms to the core and reveals that the adjustment of the monomer/initiator ratio enables control of the arm length. Size exclusion chromatography measurements show narrow molecular weight distributions. Thermal analysis reveals a lower glass transition temperature, me…

Miscibility and properties of linear poly(l-lactide)/branched poly(l-lactide) copolyester blends

2006

Abstract Polymer blends consisting of linear poly( l -lactide) (PLLA) and different proportions of dendritic PLLA-based copolyesters ( hb -PLLA) characterized by different degrees of branching (DB) were obtained in melt. The solid-state properties of poly( l -lactide)s and their blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), atomic force microscopy (AFM) and stress–strain measurements. DSC and DMA methods proved miscibility of PLLA/ hb -PLLA blends for the studied composition range. AFM indicated that no phase separation occurs in PLLA/ hb -PLLA blends and that PLLA and hb -PLLA cocrystallize in one single lamellae type. The mechanica…

Poly(isoglycerol methacrylate)-b-poly(d or l-lactide) Copolymers: A Novel Hydrophilic Methacrylate as Building Block for Supramolecular Aggregates

2010

On the basis of a new acetal-protected glycerol monomethacrylate monomer (cis-1,3-benzylidene glycerol methacrylate/BGMA) a series of potentially biocompatible and partially biodegradable homo- and block copolymers were synthesized. ATRP polymerization of BGMA yielded well-defined polyacrylates with pendant benzylidene acetal groups and high glass transition temperatures (115−130 °C). This hydrophobic poly(cis-1,3-benzylidene glycerol methacrylate) could be readily transformed into the hydrophilic and water-soluble poly(1,3-dihydroxypropyl methacrylate), referred to as poly(isoglycerol methacrylate) (PIGMA). It exclusively contains primary hydroxyl groups and therefore differs significantly…