Search

We describe the synthesis of an end-functionalized copolymer of A-(2-hydroxypropyl)methacrylamide (HPMA) and N-hydroxysuccinimide methacrylate (NMS) by reversible addition-fragmentation chain transfer (RAFT) polymerization. To control the polymer composition, the faster reacting monomer (NMS) was added slowly to the reaction mixture beginning 30 min after initating the polymerization (ca. 16% HPMA conversion). One RAFT agent, based on azocyanopentanoic acid, introduced a -COOH group to the chain at one end. Use of a different RAFT agent containing a 4-amino1,8-naphthalimide dye introduced a UV-vis absorbing and fluorescent group at this chain end. The polymers obtained had molecular weights of 30 000 and 20 000, respectively, and contained about 30 mol% NMS active ester groups. Key words: RAFT, semi-batch polymerization, dye-labeled polymer, HPMA, A-hydroxysuccinimide methacrylate. On decrit la synthase d'un copolymere fonctionnalise aux extremitesdu A-(2-hydroxypropyl)methacrylamide (HPMA) et de methacrylate de A-hydroxysuccinimide (NMS) par polymerisation impliquant une addition et une fragmentation radicalaire avec transfert de chaine (AFRT). Dans le but de controler la composition du polymere, le monomere qui reagit le plus rapidement (NMS) est additionne lentement au melange reactionnel 30 min apres que la polymerisation a ete initiee (conversion approximative de 16% du HPMA). Un agent AFRT a base d'acide azocyanopentanoique permet d'introduire un groupe -COOH a une extremite de la chaine. L'utilisation d'un agent AFRT different, contenant un colorant 4-amino-1,8-naphtalimide, introduit un groupe fluorescent et absorbant dans l'UV-vis a l'extremite de la chaine. Les polymers obtenus possedent respectivement des poids moleeculaires de 30 000 et 20 000 et ils contiennent approximativement 30 mol% de groupes esters du NMS. Mots-cles: polymerisation impliquant une addition et une fragmentation radicalaire avec transfert de chaine (AFRT), polymerization semi-discontinue, polymere marquee avec un colorant, A-(2-hydroxypropyl)methacrylamide (HPMA), methacrylate de A-hydroxysuccinimide (NMS). [Traduit par la Redaction], Introduction Poly-N-(2-hydroxypropyl)methacrylate (PHPMA) is a nontoxic, nonimmunogenic, and biocompatible polymer that offers great promise as the host carrier of polymer-drug conjugates. These conjugates (polymer therapeutics) offer some important advantages over [...]

Time-resolved fluorescence anisotropy measurements for a simple 2-substituted anthracene derivative (2-An-M) as a function of concentration in poly(methyl methacrylate) (PMMA) films is described. The results show an increased depolarization rate for samples containing a higher fraction of polymers labeled at the junction with anthracene chromophores.

The results of oxygen quenching experiments for four phosphorescent dyes [platinum octaethylporphyrin (PtOEP), platinum octaethylporphyrin ketone (PtOEPK), platinum tetrakis (pentafluorophenyl) porphyrin (PtTFPP), and Ru (dpp) 3Cl2 (dpp + 4,7-diphenyl-1, 10-phenanthroline)] in a low-glass-transition-temperature polymer matrix [poly [((n-butylamino) thionyl) phosphazene] (C4PATP) is compared. It is seen that oxygen diffusion in C4PATP obeys Fick's laws with diffusion coefficient of (3.7 + - 1.0) x 10 to the power -6 cm square s (sub -1).

The micelle exchange kinetics of hydrophobic pyrene derivatives between sodium dodecyl sulfate (SDS) and micelles are described in the presence of moderate concentrations of sodium counterions. The exchange rate is not very sensitive to the concentration of SDS micelles, except as the SDS concentration affects the ionic strength, which indicates that the kinetics are dominated by a first-order process.

We examine the nature of the chemical reactions taking place in a waterborne two‐component polyurethane formulation consisting of an acrylic polyol latex and a hydrophilically modified polyisocyanate (hmPIC) based on the trimer of hexamethylene diisocyanate. The hmPIC was diluted with 30 wt.% of an organic solvent to reduce its viscosity and formed small (~20 nm) droplets when dispersed in water. In mixtures of the polyol and hmPIC, we monitored the rate of NCO group disappearance in the dispersed state by FTIR and showed that it varied with the choice of organic solvent. We developed a method based upon 19F NMR to distinguish the reaction of the NCO groups with OH groups from the polyol from its reaction with water. FTIR measurements on films formed from these dispersions showed how the disappearance of NCO groups depended on relative humidity. In a more semi‐quantitative way, these measurements indicated the relative extent of urethane versus urea formation in these model coatings. [ABSTRACT FROM AUTHOR]

A study relating to sludge-formation processes in gasoline engine motor oil was conducted for the purpose of creating a model system that would elucidate the mechanism of such processes where small particle form and then aggregate to form sludge. The experiment involved the preparation, characterization and properties of cross-linked poly(butyl methacrylate) and poly(methyl methacrylate) latex particles containing -COOH and -CH2OH groups. Results of the study are the first step in developing the model system desired.

The dissolution characteristics of thin polymethyl methacrylate films, studied by simultaneous laser interferometry and fluorescence quenching (LIFQ) experiments, are reported. These require UV-transparent substrates. The influence of the substrate material on the LIFQ results was investigated. The results obtained with sapphire substrates allowed us to calculate the thickness of the solvent-swollen gel layer at the beginning and at the end of the dissolution process.

Pulsed field gradient nuclear magnetic resonance (PFG NMR) experiments are used for studying ligand exchange between poly(2-(N,N-dimethylamino)ethyl methacrylate) (PDMA) and trioctylphosphine oxide (TOPO) bound to the surface of CdSe/TOPO quantum dots (QDs). The studies have shown that only DMA units are directly bound to the surface and the remaining groups are present as loops or tails that protrude into the solvent and enhance the hydrodynamic diameter of the particles.

Monte Carlo simulations of resonance energy transfer experiments were studied for immobile donor and acceptor dyes confined to planar, cylindrical, and spherical restricted geometries. Euclidean spaces were examined in which the restricted geometric was a thin planar slab, a thin cylinder or cylindrical shell, or a thin spherical shell to investigate the magnitude of the coupling of the orientation parameter with the donor-acceptor separation.

Experiments that employ direct resonance energy transfer (DET) to obtain information about distances or domain sizes in polymer systems require independent information about the magnitude of the characteristic (Forster) energy transfer distance R(sub o). The experiments which determine R(sub o) values by both methods for a series of Phe-An donor-acceptro pairs in poly(methyl methacrylate) and polystyrene films are described.

The effect of concentration on photoinduced flocculation and aggregation of a nonaqueous dispersion of core-shell nanoparticles, which consist of a tightly cross-linked core composed of poly, is described. The study found that for the three different concentrations that measured average radius of gyration during aggregation scaled with time.