Bioresorbable thermoset polyester/urethane elastomers
Inventors
Concagh, Danny • Cheng You, Chang • Zugates, Greg
Assignees
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Publication Number
US-9309347-B2
Publication Date
2016-04-12
Expiration Date
Abstract
Bioresorbable thermoset elastomers and methods of making the same are disclosed. In certain embodiments, the thermoset elastomers include soft segments comprising branched polyesters, and hard segments including urethane and/or urea. The thermoset elastomers are made in certain embodiments by curing a branched prepolymer with a cross-linking agent. In certain embodiments, the mechanical properties of the thermoset elastomers are tailored by selecting the average molecular weight of the prepolymer, or by tuning the ratio of prepolymer to the cross-linking agent during curing, or by selecting a cross-linking agent with specific chemical characteristics.
Core Innovation
The invention concerns bioresorbable thermoset polyester/urethane elastomers formed from branched polyester prepolymers and isocyanate crosslinkers. The disclosed polymer has polyester soft segments and urethane/urea hard segments, wherein hydrogen bonding between hard segments contributes to strength and elastic recovery. Prepolymers include poly(glycolide-co-̂-caprolactone) and poly(lactide-co-̂-caprolactone), reacted with symmetrical isocyanate crosslinkers such as hexamethylene diisocyanate and lysine diisocyanate.
Mechanical properties are adjustable through prepolymer molecular weight, crosslink density, and crosslinker structure, with catalyst selection influencing degradation rate. Disclosed formulations demonstrate high elongation, differentiated tear strength based on crosslinker selection, and stent-coating integrity following crimping. The patent disclosure focuses on these elastomeric compositions and their corresponding structural properties.
Claims Coverage
The relevant claims include two independent claims covering elastomeric polymers prepared using branched polyester or prepolymer and an isocyanate crosslinker, comprising two inventive features.
Elastomer made from a branched polyester and symmetrical isocyanate crosslinker
The claim covers an elastomer prepared by at least partially crosslinking a branched polyester with a symmetrical isocyanate crosslinker. The polyester has at least three branches, a glass transition temperature below about 25C, and a specified minimum average molecular weight.
Polymer made by curing a branched prepolymer with an isocyanate crosslinker
The claim covers a polymer prepared by curing an isocyanate crosslinker with a branched prepolymer. The prepolymer has at least three branches, a glass transition temperature below about 25C, and an average molecular weight within a defined range.
The independent claims cover elastomeric polymers based on branched polyester or prepolymer and isocyanate crosslinking, with specified structural and material-property requirements.
Stated Advantages
The disclosed elastomers exhibit strength and elastic recovery associated with hard segments and hydrogen bonding between them.
Hexamethylene diisocyanate-crosslinked films provide higher tear strength than lysine diisocyanate-crosslinked films.
Hexamethylene diisocyanate coatings maintain integrity on stents after crimping, avoiding cracking observed in lysine diisocyanate coatings.
The disclosed elastomers achieve elongation at break extending up to 940%.
Documented Applications
Coatings for stents.
Vascular grafts.
Drug delivery.
Tissue-engineering scaffolds.
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