Abstract: Poly(ethylene glycol) (PEG), a highly biocompatible hydrophilic polyether, is tethered to poly(propylene fumarate) (PPF), a biodegradable polyester. To avoid change in molecular weight distribution of PPF, end hydroxyl groups of PPF are reacted with bis-carboxymethyl PEG after being treated with thionyl chloride. New end carboxyl groups of the PEG-tethered PPF are further reacted with N-hydroxysuccinimide (NHS) in the presence of dicyclohexylcarbodiimide (DCC) to couple bioactive molecules. Glutamine and glycine-arginine-glycine-aspartic acid (GRGD) are attached to the PEG-tethered PPF in 50 mM phosphate buffer of pH of 7.4. The method is valuable for the preparation of a triblock copolymer with PEG end blocks and the coupling of biologically active molecules.

Abstract: A method for controlling the gel point of a bone cement containing poly(polypropylene fumarate), a cross-linking monomer, an initiator, an inorganic filler, and a radical initiator. The gel point is controlled by varying the molecular weight of the poly(polypropylene fumarate) while maintaining the weight average molecular weight (M.sub.w) of the poly(polypropylene fumarate) above 2000 and the polydispersity index of the poly(polypropylene fumarate) below 2. In a preferred embodiment, the molecular weight of the poly(polypropylene fumarate) greater than 4000, and more preferably greater than 5000.

Abstract: An electromagnetic levitator is disclosed, comprising: a plurality of longitudinal sections formed from a conducting material and arranged around a longitudinal axis. The longitudinal sections are connected to a power source such that when the levitator is in operation, current flowing through adjacent longitudinal sections creates opposing magnetic fields. The levitator has first and second ends defining a levitation zone therebetween. When alternating current is passed through the conductors, a levitation tunnel is formed in the levitation zone, with the levitation tunnel having zero magnetic flux density along its center and non-zero magnetic flux density at all other points.