Enhanced Mechanical and Shape Memory Properties of Poly(propylene glycol)‐Based Star‐Shaped Polyurethane

Abstract

A poly(propylene glycol)‐based star‐shaped thermoplastic shape memory polyurethane elastomer (STPU) is synthesized by bulk polymerization with the addition of trifunctional poly‐propylene glycerol (PPG‐3) to improve the mechanical and shape memory properties. The mechanical properties are enhanced significantly with the addition of PPG‐3. The tensile strength of STPU is up to 36.0 MPa, which is almost two times higher than that of linear polyurethane (18.4 MPa). The star‐shaped structure, reduction in microphase separation, and good phase compatibility of STPU are the reasons for the enhancement of mechanical properties. The branching degree of STPU (up to 1.83) is much higher than that of linear polyurethane (0.5). STPU shows higher shape memory fixity ratio (97.2%) at −10 °C and recovery ratio (96.7%) at 40 °C than TPU. Therefore, the design and synthesis of star‐shaped polyurethane is an effective approach for improving the mechanical and shape memory properties of polyurethane elastomer.

Biostable Segmented Thermoplastic Polyurethane Shape Memory Polymers for Smart Biomedical Applications

“…Although the synthesized STPUs exhibited shape memory properties, their degradation and shape stability during degradation were not reported . In the star and linear systems developed by Xu et al and Peng et al, respectively, PPG was incorporated in a system with MDI as the hard segment and BD as the chain extender. Products had high transition temperatures and appropriate mechanical and shape memory properties, but cell viability and degradation profiles in hydrolytic and oxidative media were not provided .…”

“…In the star and linear systems developed by Xu et al and Peng et al, respectively, PPG was incorporated in a system with MDI as the hard segment and BD as the chain extender. Products had high transition temperatures and appropriate mechanical and shape memory properties, but cell viability and degradation profiles in hydrolytic and oxidative media were not provided . In another work, Candau et al produced a strain-induced SMP with poly­(ethylene oxide) (PEO; soft segment), bis­(4-isocyanatocyclohexyl) methane (HMDI; hard segment), and 2-methyl-1,5-diaminopentane (MDAP; chain extender).…”

“…21 TEG was employed as the chain extender in this STPU system to confer required mechanical properties 22 and stability in oxidative degradation media. 23 PPG has been used in many studies, but none of the previously developed systems were able to fulfill all requirements for a cytocompatible, biostable STPU with required mechanical properties, 24 high transition temperatures to enable shape stability in 37 °C water, 27 and/or minimal shape changes in degradation media 25,26 For example, Xu et al developed a system based on PPG with 4,4′-diphenylmethane diisocyanate (MDI) as the hard segment and 1,4-butanediol (BD) as the chain extender. They reinforced the resulting polymer with inorganic moieties.…”

“…Products had high transition temperatures and appropriate mechanical and shape memory properties, but cell viability and degradation profiles in hydrolytic and oxidative media were not provided. 26 In another work, Candau et al produced a strain-induced SMP with poly(ethylene oxide) (PEO; soft segment), bis(4isocyanatocyclohexyl) methane (HMDI; hard segment), and 2-methyl-1,5-diaminopentane (MDAP; chain extender). This system had a low transition temperature (around 34 °C); therefore, the polymer could not maintain its temporary shape upon implantation.…”

Water-responsive shape memory thermoplastic polyurethane scaffolds triggered at body temperature for bone defect repair

“…Commonly, the cooling temperature in shape memory testing was 10 1C less than the transition temperature. [38][39][40] For example, Yuan et al 38 selected the cooling temperature for the deformed TPU specimen at room temperature, which was around 10 1C less than the transition temperature, while the results indicated that the shape fixation ratio of the specimen was only around 25%. Many present studies have demonstrated that the shape fixation ratio can be improved at lower cooling temperatures.…”