Biodegradable Polyurethane Ureas with Variable Polyester or Polycarbonate Soft Segments: Effects of Crystallinity, Molecular Weight, and Composition on Mechanical Properties

Abstract

Biodegradable polyurethane urea (PUU) elastomers are ideal candidates for fabricating tissue engineering scaffolds with mechanical properties akin to strong and resilient soft tissues. PUU with a crystalline poly(ε-caprolactone) (PCL) macrodiol soft segment (SS) showed good elasticity and resilience at small strains (<50%), but showed poor resilience under large strains due to stress-induced crystallization of the PCL segments, with a permanent set of 677±30% after tensile failure. To obtain softer and more resilient PUUs, noncrystalline poly(trimethylene carbonate) (PTMC) or poly(δ-valerolactone-co-ε-caprolactone) (PVLCL) macrodiols of different molecular weights were used as SSs that were reacted with 1, 4-diisocyanatobutane and chain extended with 1, 4-diaminobutane. Mechanical properties of the PUUs were characterized by tensile testing with static or cyclic loading and dynamic mechanical analysis. All the PUUs synthesized showed large elongations at break (800–1400%) and high tensile strength (30–60 MPa). PUUs with non-crystalline SSs all showed improved elasticity and resilience relative to the crystalline PCL-based PUU, especially for the PUUs with high molecular weight SSs (PTMC 5400 Mn and PVLCL 6000 Mn), of which the permanent deformation after tensile failure was only 12±7% and 39±4%, respectively. The SS molecular weight also influenced the tensile modulus in an inverse fashion. Accelerated degradation studies in PBS containing 100 U/mL lipase showed significantly greater mass loss for the two polyester-based PUUs versus the polycarbonate-based PUU, and for PVLCL versus PCL polyester PUUs. Basic cytocompatibility was demonstrated with primary vascular smooth muscle cell culture. The synthesized families of PUUs showed variable elastomeric behavior that could be explained in terms of the underlying molecular design and crystalline behavior. Depending upon the application target of interest, these materials may provide options or guidance for soft tissue scaffold development.

Thermal and mechanical properties of polyurethanes modified with L-ascorbic acid

“…Chattopadhyay et al [39] related lower values of storage modulus with the lower tensile strength of the material. On the other hand, decrease in storage modulus and loss modulus with the increase in the filler amount was correlated interactions of modifier with PUR matrix, which impact on the thermomechanical properties of obtained PURs [37,40].…”

“…Determined tensile strength of such ascorbic acid-filled polyurethanes was 47.75 ± 16.70 MPa, which is significantly higher than in case of PURs described in this paper. In the literature data there are many reports of biomedical PURs mechanical studies [37]. For example Dey et al performed urethanedoped polyesters of tensile strength in the range of 14.6 ± 1.0-41.07 ± 6.9 MPa and elongation at break of 337.0 ± 6.0 % [36]; Guan et al obtained poly(ester urethane)ureas and poly(ether-ester urethane) ureas with the use of polycaprolactone polyester or bloc copolymer of poycaprolactone and polyethylene glycol soft segments and 1,4-diisocyanatobutane and putrescine derived hard segments.…”

Assessment of aliphatic poly(ester-carbonate-urea-urethane)s potential as materials for biomedical application

“…Compared to poly(carbonate-urea-urethane)s obtained in the same manner, but lacking modification with the ester derivative, the samples had much higher elongations at break and higher ), have shown tensile strengths of 11.7, 3.0, and 22.7 MPa, respectively [43]. Samples based on oligo(δ-valerolactone-co-ε-caprolactone) diol, BDI and putrescine exhibited similar tensile strength, but much higher elongation at break, around 1300% [44]. In comparison to poly(ester-carbonate-urea-urethane)s described by Hong et al [42], which were synthesized from oligo(ε-caprolactone) and oligo(1,6-hexamethylene carbonate) diols, tetramethylene diisocyanate, and putrescine, our samples exhibited higher values of tensile strengths and simultaneously were characterized by lower elongation at break.…”

Synthesis and structure-property relationships of biodegradable polyurethanes

“…PUUs with crystalline PCL SS had much higher permanent deformation than those with non-crystalline SS of PTMC or PVLCL. Initial moduli were mainly dependent on SS molecular weight, with higher SS associated with a lower initial modulus [78]. PUUs with noncrystalline SS all showed improved elasticity and resilience relative to crystalline PCL-based PUUs, especially for PUUs with high molecular weight SS (PTMC, M n = 5400 g mol −1 and PVLCL, M n = 6000 g mol −1 ), of which the permanent deformation after tensile failure was only 12 ± 7 % and 39 ± 4 %, respectively.…”

“…Figure 3. DSC analysis of (a) PUUs and (b) stretched PUU-PCL2000 (permanent deformation of 677%) with temperature change [78] Recently, biodegradable PCL/PU has been synthesized by curing with water.…”