Polyaxial initiators

Shalaby, S. W., Amorphous Polymeric Polyaxial Initiators and Compliant Crystalline Copolymers Thereof, U.S. Patent (to Poly-Med, Inc.), 6,462,169, 2002. 

The amorphous polymeric, polyaxial initiators (PPIs) used in these systems to produce crystalline absorbable copolymeric materials can be made by reacting a cyclic monomer or a mixture of cyclic monomers such as trimethylene carbonate, caprolactone, and l,5-dioxapane-2-one in the presence of an organometallic catalyst with one or more polyhydroxy, polyamino, or hydroxyamino compounds having three or more reactive amines and/or hydroxyl groups. Typical examples of the latter compounds are glycerol and ethane-trimethylol, propane-trimethylol, pentaerythritol, triethanolamine, and N-2-aminoethyl-l,3-propanediamine. 

In a study by Carpenter and co-workers, two types of copolyesters were made to determine the effect of a basic central group on the properties of the polymer.il Accordingly, triethanolamine (TEA) and trimethylolpropane (TMP) were used to prepare the polyaxial initiator with central amine and carbon atoms, respectively, using trimethylene carbonate (TMC) and capro-lactone (CL) as comonomers. 

Minor changes in the polymeric polyaxial initiator composition on the hydrolytic stability of the polyaxial end-grafted system ... 

Crystalline copolyesters made by end-grating crystallizable segments onto amorphous polyaxial initiators exhibit a lower overall degree of crystallinity but higher tendency to crystallize from the melt into smaller crystallites as compared to their linear coimterparts. The polyaxial polymers are more suitable than linear ones for developing high-impact, more compliant biomedical devices as compared with their linear counterparts. 

Contributions of the Polyaxial Chain Configuration and Composition of Polymeric Initiators to Thermal... 

Certain polyaxial copolymers can be converted to compliant monofilaments with comparable, or superior, initial strength relative to surgical gut sutures. 

Using polyaxial polymeric initiators on the thermal properties of crystalline end-grafted products as compared with those having linear molecules... 

Composition of the amorphous initiator for the polyaxial crystalline systems can be easily adjusted to provide biomaterials for constructing devices with a broad range of strength retention profiles. 

Segmented copolymers geared for the production of compliant monofilament sutures described in Chapter 3 dealt with the use of end-grafting of an amorphous, or low melting, polyaxial polymeric initiator with cyclic monomers to form crystalline end-grafts. In this particular chain design, the... 

Environmental stress cracking is the failure in surface-initiated brittle fracture of a polyethylene specimen, or a part under polyaxial stress, in contact with a medium in the absence of which fracture does no occur under the same conditions of stress. Combinations of external and/or internal stresses may be involved, and the sensitizing medium may be gaseous, liquid, semisolid, or solid. 

---