A series of blends of poly(ethylene glycol) (PEG) with different molecular weights with: (i) capric, (ii) lauric, (iii) myristic, (iv) palmitic or (v) stearic acid, as a thermal energy storage material, has been investigated by differential scanning calorimetry (DSC). Transition temperatures and latent heat of transition of PEG, fatty acids and their binary blends were determined since these properties are of primary importance in the design of phase change energy storage materials. The experimental results showed that it is possible to obtain homogeneous (as indicated by DSC data) polymer/fatty acid blends by mixing in the melt and subsequent solidification. The melting ranges of PEG/fatty acid systems were observed to be from 30 to 72 °C while their heat of transition lies in the range of 168–208 J · g?1. Synergistic action of the components was found for PEG 10 000/stearic acid blend – heat of transition was ca. 15 and 35% higher than for pure stearic acid and PEG, respectively. This phenomena may be explained in terms of strengthened specific interactions via hydrogen bonding leading to formation of more perfect crystalline lattice.
We report a simple and rapid method to prepare extremely bright, functionalized, stable, and biocompatible conjugated polymer nanoparticles incorporating functionalized polyethylene glycol (PEG) lipids by reprecipitation. These nanoparticles retain the fundamental spectroscopic properties of conjugated polymer nanoparticles prepared without PEG lipid, but demonstrate greater hydrophilicity and quantum yield compared to unmodified conjugated polymer nanoparticles. The sizes of these nanoparticles, as determined by TEM, were 21-26 nm. Notably, these nanoparticles were prepared with several PEG lipid functional end groups, including biotin and carboxy moieties that can be easily conjugated to biomolecules. We have demonstrated the availability of these end groups for functionalization using the interaction of biotin PEG lipid conjugated polymer nanoparticles with streptavidin. Biotinylated PEG lipid conjugated polymer nanoparticles bound streptavidin-linked magnetic beads, while carboxy and methoxy PEG lipid modified nanoparticles did not. Similarly, biotinylated PEG lipid conjugated polymer nanoparticles bound streptavidin-coated glass slides and could be visualized as diffraction-limited spots, while nanoparticles without PEG lipid or with non-biotin PEG lipid end groups were not bound. To demonstrate that nanoparticle functionalization could be used for targeted labelling of specific cellular proteins, biotinylated PEG lipid conjugated polymer nanoparticles were bound to biotinylated anti-CD16/32 antibodies on J774A.1 cell surface receptors, using streptavidin as a linker. This work represents the first demonstration of targeted delivery of conjugated polymer nanoparticles and demonstrates the utility of these new nanoparticles for fluorescence based imaging and sensing. 相似文献
Injectable biodegradable copolymer hydrogels, which exhibit temperature-responsive sol-to-gel transition, have recently drawn much attention as promising biomedical materials such as drug delivery, cell implantation, and tissue engineering. These injectable hydrogels can be implanted in the human body with minimal surgical invasion. Temperature-responsive gelling copolymers usually possess block- and/or branched architectures and amphiphilicity with a delicate hydrophobic/hydrophilic balance. Poly(ethylene glycol) (PEG) has typically been used as hydrophilic segments due to its biocompatibility and temperature-dependent dehydration nature. Aliphatic polyesters such as polylactide, poly(lactide-co-glycolide), poly(ε-caprolactone), and their modified copolymers have been used as hydrophobic segments based on their biodegradability and biocompatibility. Copolymers of PEG with other hydrophobic polymers such as polypeptides, polydepsipeptides have also been recently reported as injectable hydrogels. In this review, brief history and recent advances in injectable biodegradable polymer hydrogels are summarized especially focusing on the relationship between polymer architecture and their gelation properties. Moreover, the applications of these injectable polymer gels for biomedical use such as drug delivery and tissue engineering are also described. 相似文献
Summary
New lactide-based poly(ethy1ene glycol) (PEG) polymer networks (GL-PEG) have been prepared by photopolymerization using two
nontoxic niacromers, triacrylated lactic acid oligomer emanating from a glycerol center (GL) and monoacrylated PEG. These
materials may use as polymer scaffolds in tissue engineering because they provide biodegradable, cell-adhesion resistant,
and ligand-immobilizable characteristics. The thermal and mechanical properties of the resulting GL-PEG networks were evaluated
and their biodegradability was investigated in phosphate buffered saline (PBS) at 80°C. The glass transition temperature (Tg)
of all networks after degradation relatively decreased and the trend was similar to those before biodegradation, whereas thermal
decomposition temperature (Td1/2) increased in all networks to a certain degree. The tensile strength decreased as PEG was incorporated and as the molecular
weight and content of PEG increased due to the soft PEG chains. Degradation rate of GL-PEG networks was controlled by the
ratio of GL to PEG, and generally the rate of GL-PEG networks was faster than that of GL homonetworks.
Received: 29 November 2002/Revised version: 5 February 2003/Accepted: 11 February 2003
Correspondence to Dong Keun Han 相似文献
Disulfonated poly(arylene ether sulfone) (BPS) random copolymers, prepared from a sulfonated monomer, have been considered for use as membrane materials for various applications in water purification and power generation. These membranes can be melt-processed to avoid the use of hazardous solvent-based processes with the aid of a plasticizer, a low molecular weight poly(ethylene glycol) (PEG). PEG was used to modify the glass transition temperature and melt rheology of BPS to enable coextrusion with polypropylene (PP). Our previous paper discussed the miscibility of BPS with PEG and the influence of PEG on the glass transition of BPS. In this study, the rheological properties of disulfonated poly(arylene ether sulfone)s plasticized with poly(ethylene glycol) (PEG) are investigated to identify coextrusion processing conditions with candidate PPs. The effects of various factors including PEG molecular weight, PEG concentration, temperature and BPS molecular weight on blend viscosity were studied. The rheological data effectively lie on the same master curve developed by Bueche and Harding for non-associating polymers such as poly(methyl methacrylate) (PMMA) and polystyrene (PS). Although sulfonated polysulfone contains ionic groups, the form of its viscosity versus shear rate (or frequency) behavior appears to be dominated by the relaxation of polymer entanglements. 相似文献