Effect of the hard segment chemistry and structure on the thermal and mechanical properties of novel biomedical segmented poly(esterurethanes)

Abstract

Two series of biomedical segmented polyurethanes (SPU) based on poly(epsilon-caprolactone) diol (PCL diol), 1,6-hexamethylene diisocyanate (HDI) or L: -lysine methyl ester diisocyanate (LDI) and three novel chain extenders, were synthesized and characterized. Chain extenders containing urea groups or an aromatic amino-acid derivative were incorporated in the SPU formulation to strengthen the hard segment interactions through either bidentate hydrogen bonding or pi-stacking interactions, respectively. By varying the composition of the hard segment (diisocyanate and chain extender), its structure was varied to investigate the structure-property relationships. The different chemical composition and symmetry of hard segment modulated the phase separation of soft and hard domains, as demonstrated by the thermal behavior. Hard segment association was more enhanced by using a combination of symmetric diisocyanate and urea-diol chain extenders. The hard segment cohesion had an important effect on the observed mechanical behavior. Polyurethanes synthesized using HDI (Series H) were stronger than those obtained using LDI (Series L). The latter SPU exhibited no tendency to undergo cold-drawing and the lowest ultimate properties. Incorporation of the aromatic chain extender produced opposite effects, resulting in polyurethanes with the highest elongation and tearing energy (Series H) and the lowest strain at break (Series L). Since the synthesized biodegradable SPU possess a range of thermal and mechanical properties, these materials may hold potential for use in soft tissue engineering scaffold applications.

Mechanical behavior of bilayered small-diameter nanofibrous structures as biomimetic vascular grafts

“…A bioresorbable SPEU named PHD was synthesized from aliphatic diisocyanate, aliphatic polyester, and a diester-diphenol chain extender according to previously reported procedures (Caracciolo et al, 2009). Dichloromethane (DCM) and N,N-dimethylformamide (DMF) were acquired from Anedra (BA, Argentina).…”

Synthesis and structure-property relationships of biodegradable polyurethanes

“…Caracciolo et al [20] reported the preparation of two series of biomedical segmented polyurethanes (SPU) based on PCL, HDI or LDI and three different chain extenders. Chain extenders containing urea groups or an aromatic amino-acid derivative were incorporated in the SPU formulation to strengthen the hard segment interactions through either bidentate hydrogen bonding or π-stacking interactions, respectively.…”

“…Here it should be noted that several reactants commonly used in PU formulations such as, for example, 4,4'-diisocyanatodiphenylmethane (MDI) or 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA or MBOCA), degrade to toxic products and therefore have to be excluded from the synthesis of BioPUs. The choice of reactants in order to obtain polymers with non-toxic degradation products, which will give a medical implant with good mechanical properties, is the main challenge of the production of novel BioPUs [18][19][20]. The development of properly biodegradable PU materials with appropriate mechanical and target functional properties (e.g.…”

Aplicaciones de la tecnología de radiación de microondas en la síntesis de biomateriales

“…Otros investigadores también reportaron la síntesis de PUs biorreabsorbibles usando extensores de cadena novedosos [121][122][123]. A pesar de su rol central, la síntesis de PUs asistida por esta tecnología ha sido estudiada de forma muy limitada y la mayoría de los estudios se centraron principalmente en los aspectos químicos de la vía de síntesis y las características moleculares obtenidas.…”