Hyperbranched Polyester (hyperbranched + polyester)

Distribution by Scientific Domains


Selected Abstracts


Broadband dielectric spectroscopy on the molecular dynamics in different generations of hyperbranched polyester

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009
Gamal Turky
Abstract Dielectric spectroscopy (10,2 Hz to 106 Hz) was employed to investigate the molecular dynamics of hyperbranched polyesters where the number of the generation is systematically varied from 2 to 5. As a first result, the dielectric properties depends strongly on the generation of the hyperbranched polymers. For higher generations (3 to 5) at temperatures below Tg two relaxation processes are observed, a ,-process at lower temperatures and a ,-process at higher ones. The apparent activation energies are around 100 kJ/mol which seems to be too high for truly localized processes. For the Generation 2, only the ,-process is observed. For all investigated polymers the dielectric ,-relaxation could not be observed because of strong conductivity effects. Therefore, the conductivity is systematically analyzed which obeys the peculiarities found to be characteristic for semiconducting disordered materials. Especially, the Barton/Nakajima/Namikawa relationship is found to be valid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]


Encapsulation and Controlled Release of a Hydrophobic Drug Using a Novel Nanoparticle-Forming Hyperbranched Polyester,

MACROMOLECULAR BIOSCIENCE, Issue 7 2005
Jianhua Zou
Abstract Summary: An amphiphilic, hyperbranched polymer suitable for use in controlled drug delivery is reported. This polymer was obtained by modification of the hyperbranched aliphatic polyester Boltorn‘ H20 (H20) with succinic anhydride and then glycidyl methacrylate, and formed nanoparticles in aqueous solution. The critical association concentration was 7.4,◊,10,3 g,∑,L,1, as determined by fluorescence spectroscopy using pyrene as a molecular probe. A static/dynamic laser light scattering (LLS) study revealed that the average particle size was 39.4 nm with a low particle size distribution (PDI = 0.04), and that each particle was composed of about 350 amphiphilic molecules. Daidzein, a hydrophobic traditional Chinese medicine, was encapsulated during particle formation and the release properties were determined. The optimal feeding concentration of daidzein to hyperbranched polyester was 4.9,◊,10,5 g,∑,mL,1 to 5.0,◊,10,3 g,∑,mL,1 with a loading efficiency of 76.1%. In the presence of the enzyme Lipase PS, the drug loaded nanoparticles degraded in a random one-by-one manner and released the drug over a few days. This system is therefore a novel controlled drug release system based on nanoparticles formed of hyperbranched polyester. Encapsulation of daidzein by hyperbranched polyester particles. [source]


Synthesis of Fluorinated Hyperbranched Polymers and Their Use as Additives in Cationic Photopolymerization

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2005
Marco Sangermano
Abstract Summary: A fluorine containing hyperbranched polymer was synthesized by modifying an aromatic-aliphatic hyperbranched polyester with a semifluorinated alcohol via a Mitsunobu reaction and was subsequently used as an additive in cationic photopolymerization of an epoxy resin. The remaining OH groups of the fluorinated hyperbranched polymer interact with the polymeric carbocation through a chain-transfer mechanism inducing an increase in the final epoxy conversion. The fluorinated HBP induces modification of bulk and surface properties, with an increase in Tg and surface hydrophobicity already reached at very low concentration. The HBFP additive can, therefore, protect the coatings from aggressive solvents, increases hardness, and allows the preparation of a low energy surface coating. Synthesis of fluorinated hyperbranched polyester. [source]


Thermomechanical and morphological properties of epoxy resins modified with functionalized hyperbranched polyester

POLYMER ENGINEERING & SCIENCE, Issue 11 2006
I. Blanco
Thermomechanical and morphological properties of blends of epoxy monomers and hydroxyl and epoxy functionalized hyperbranched polyesters have been studied. Different properties of the blends were found by changing the cure cycles (a precure step followed by a postcure at higher temperature). All the blends showed phase separation with a particulate morphology. Through the addition of the hydroxyl-ended modifiers, rather than the epoxy-ended, an increase of the viscosity and of the reactivity of the uncured blends was obtained. The blends containing the epoxy functionalized polymer showed some liquid,liquid transitions in the rheological traces, probably because of the phase separation phenomena. POLYM. ENG. SCI., 46:1502,1511, 2006. © 2006 Society of Plastics Engineers [source]


Broadband dielectric spectroscopy on the molecular dynamics in different generations of hyperbranched polyester

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009
Gamal Turky
Abstract Dielectric spectroscopy (10,2 Hz to 106 Hz) was employed to investigate the molecular dynamics of hyperbranched polyesters where the number of the generation is systematically varied from 2 to 5. As a first result, the dielectric properties depends strongly on the generation of the hyperbranched polymers. For higher generations (3 to 5) at temperatures below Tg two relaxation processes are observed, a ,-process at lower temperatures and a ,-process at higher ones. The apparent activation energies are around 100 kJ/mol which seems to be too high for truly localized processes. For the Generation 2, only the ,-process is observed. For all investigated polymers the dielectric ,-relaxation could not be observed because of strong conductivity effects. Therefore, the conductivity is systematically analyzed which obeys the peculiarities found to be characteristic for semiconducting disordered materials. Especially, the Barton/Nakajima/Namikawa relationship is found to be valid. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]


Hyperbranched polyesters and their application in dental composites: monomers for low shrinking composites

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2001
J. E. Klee
Abstract Using trimethylolpropane (TMP) and 2,2-bishydroxymethylpropionic acid (Bis-MPA), aliphatic hyperbranched polyesters (HBP) were synthesized, with a degree of branching of DB,=,0.47 and a degree of polymerization of Pn,=,16.5. Aromatic HBPs with repetitive units of 2,2-bis(4-hydroxyphenyl)pivalonic acid (Bis-PVA) lead to a higher DB,=,0.48 and Pn,=,30.5 compared to the aliphatic HBP. Reactive functionalization of the hyperbranched polymers was achieved via esterification of mixtures of methacrylic acid and carboxylic acids. In this manner, i -butyric acid and methacryloyl terminated HBPs were obtained. They have a low viscosity ranging from 200 to 364,Pa*s and exhibit relatively low volume shrinkage (1.9 to 3.6%) during photoinitiated cure. Dental composites with volume shrinkage of 0.5 to 1.5% have been prepared using these methacryloyl terminated HBPs in combination with a Ba/alumosilicate glass filler. Copyright © 2001 John Wiley & Sons, Ltd. [source]