Hydrogel Nanoparticles in Drug Delivery

A very straightforward approach was developed to synthesize pegylated thermoresponsive core-shell nanoparticles in a minimum of steps, directly in water. It is based on RAFT-controlled radical crosslinking copolymerization of N,N-diethylacrylamide (DEAAm) and N,N′-methylene bisacrylamide (MBA) in aqueous dispersion polymerization. Because DEAAm is water-soluble and poly(N,N-diethylacrylamide) (PDEAAm) exhibits a lower critical solution temperature at 32 °C, the initial medium was homogeneous, whereas the polymer formed a separate phase at the reaction temperature. The first macroRAFT agent was a surface-active trithiocarbonate based on a hydrophilic poly(ethylene oxide) block and a hydrophobic dodecyl chain. It was further extented with N,N-dimethylacrylamide (DMAAm) to target macroRAFT agents with increasing chain length. All macroRAFT agents provided excellent control over the aqueous dispersion homopolymerization of DEAAm. When they were used in the radical crosslinking copolymerization of DEAAm and MBA, the stability and size of the resulting gel particles were found to depend strongly on the chain length of the macroRAFT agent, on the concentrations of both the monomer and the crosslinker, and on the process (one step or two steps). The best-suited experimental conditions to reach thermosensitive hydrogels with nanometric size and well-defined surface properties were determined. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2373–2390, 2009

Pegylated thermally responsive block copolymer micelles and nanogels via in situ RAFT aqueous dispersion polymerization

Control of polymerization shrinkage and stress in nanogel-modified monomer and composite materials

A phenolic group containing hyperbranched polyester (HBP) was synthesized and employed as chain transfer agent in cationic photopolymerization of a biscycloaliphatic epoxy monomer (CE). The epoxy group conversion increases by increasing the amount of HBP in the photocurable resin, due to a chain transfer reaction involving the phenolic-OH groups. HBP acts as a plasticizer inducing decrease of the T g values together with an increase of the toughness properties. Meanwhile gel content increases together with the E' values. By increasing the amount of HBP in the photocurable resin an increase of the density is evident indicating a decrease of free volume. Therefore an improvement of the gas barrier properties might be expected; at the same time an increase of the thermal stability is evident.

Phenolic Hyperbranched Polymers as Additives in Cationic Photopolymerization of Epoxy Systems

An emulsion-polymerized addition copolymer formed from a monomer mixture comprising ethylenically unsaturated monomers including from more than 4 to 15 wt % based on the weight of said mixture of at least one ethylenically unsaturated carboxylic acid functional monomer, and from 0.05 to 5 wt % based on the weight of said mixture of at least one polymerizable surfactant monomer comprising hydrophobic and hydrophilic functional groups, wherein said hydrophobic functional group comprises a polymerizable group within it, is useful as a binder in an ink jet ink having improved print quality.

Polymeric binders for ink jet inks

Cross-linked particles having a size ranging from 10-300 nm, obtained by polymerization in a dispersion in a non-aqueous, non-solvent medium of the formed polymer of a composition consisting of unsaturated ethylenically polymerizable compounds, comprising: at least one monomer (A), comprising one single ethylenicunsaturation, whereby the microparticles formed in said non-aqueous medium are autostablilized during and after polymerization without any other addition of a polymer having a stabilizing agent function either before, during or after polymerization; at least one compound (B) comprising at least two ethylenic unsaturations and, optionally according to the cases in question, at least one compound (C) comprising one single ethylenic unsaturation and/or at least one compound (D) which is different from A, B and C and comprising at least one ethylenic unsaturation that can be radically polymerized and at least one second reactive function (f1) that is different from an ethylenic unsaturation.

Cross-linked microparticles, method for the production and use thereof

Acrylate-functionalized copolymers were synthesized by the modification of poly(butyl acrylate-co-glycidyl methacrylate) (BA/GMA) and poly(butyl acrylate-co-methyl methacrylate-co-glycidyl methacrylate). 13C-NMR analyses showed that no glycidyl methacrylate block longer than three monomer units was formed in the BA/GMA copolymer if the glycidyl methacrylate concentration was kept below 20 mol %. We chemically modified the copolymers by reacting the epoxy group with acrylic acid to yield polymers with various glass-transition temperatures and functionalities. We studied the crosslinking reactions of these copolymers by differential scanning calorimetry to point out the effect of chain functionality on double-bond reactivity. Films formed from acrylic acrylate copolymer precursors were finally cured under ultraviolet radiation. Network heterogeneities such as pendant chains and highly crosslinked microgel-like regions greatly influenced the network structure and, therefore, its viscoelastic properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 753–763, 2002

Synthesis and photopolymerization of acrylic acrylate copolymers

The invention relates to thermosetting compositions, especially for coverings or moulding purposes, comprising cross-linked polymer microparticles having a size ranging from 10 - 300 nm and including at least one reactive function that can react with at least one of the reactive compounds of the thermosetting composition. Preferably,said microparticles have at least a second reactive function that is distinct from the first and able to react with at least one other function of the first type contained by another microparticle and/or by a reactive constituent of the thermosetting composition. The microparticles are at least partially soluble and can be mixed and/or dispersed in the initial thermosetting composition. The preferred thermosetting compositions are of the epoxy/amine resin based variety or are based on unsaturated polyester resins and/or vinyl ester resins. The coverings or moulded objects thus obtained exhibit very good mechanical, thermal and chemical strength as a result of the presence of said particles.

Thermosetting resin compositions comprising cross-linked reactive microparticles with improved mechanical strength

(Meth)acrylic cross-linked polymer micro-particles have been synthesized by dispersion polymerization in organic media. They were produced by radical copolymerization of mono(meth)acrylate monomers with a certain concentration of a diacrylate as cross-linker, in a mixture of two organic solvents, heptane and propan-2-ol. The reactive surfactant (surfmer) was a low solubility parameter acrylate monomer, based on an aliphatic ester group (generally C 18 ) or an isobornyl cycle, which gave auto-dispersing character to the microparticles. By using glycidyl methacrylate in the monomer mixture, oxirane groups were introduced in the particles. The influence of the major synthesis parameters such as solvent composition, monomer composition and concentration, and initiator concentration has been investigated regarding the size and the molar mass of the cross-linked polymer microparticles. The study was completed with the influence of the nature and the concentration of the surfmer, the concentration of cross-linking agent and the composition of monomers feed. Stable cross-linked microparticles ranging from z-average radius of gyration, R z = 20 nm to R z > 60 nm were obtained by varying the synthesis conditions. The smallest microparticles were prepared with a blend of heptane and propan-2-ol in the 50/50 ratio by weight. Increasing the surfmer concentration or reducing the monomer concentration in the reaction mixture usually led to smaller microparticles. The longer the aliphatic chain of the surfmer, the smaller the microparticles. Minimum sizes were obtained for cross-linking agent concentrations between 5 and 7.5 mol-%, depending on monomers composition. For higher concentrations, macrogelation may occur during the synthesis.

(Meth)acrylic Cross-Linked Polymer Microparticles: Synthesis by Dispersion Polymerization and Particle Characterization

Criteria for the preparation of cross-linked poly(meth)acrylate microparticles by solution free radical polymerization

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