The return of a forgotten polymer—Polycaprolactone in the 21st century

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Degradable Controlled-Release Polymers and Polymeric Nanoparticles: Mechanisms of Controlling Drug Release

Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications.

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Biomedical Applications of Biodegradable Polymers

Magnetocaloric effect: From materials research to refrigeration devices

Recent trends in biodegradable polymers indicate significant developments in terms of novel design strategies and engineering to provide advanced polymers with comparably good performance. However, there are several inadequacies in terms of either technology or cost of production especially in the case of applications in environmental pollution. So, there is a need to have a fresh perspective on the design, properties and functions of these polymers with a view to developing strategies for future developments. The paper reviews the present state-of-art on biodegradable polymers and discusses the salient features of the design and properties of biodegradable polymers. Special emphasis is given to the problems and prospects of (1) approaches adopted to make non-biodegradable synthetic polymers such as polyethylene biodegradable and (2) biodegradable polymers and copolymers made from renewable resources especially poly(lactic acid) based polymers and copolymers which are emerging as the candidate biodegradable materials for the future.

Biodegradable Polymers- A Review on Recent Trends and Emerging Perspectives

The effect of Fe content on hardness and toughness of Ni48.7Mn30.1−xFexGa21.2 (x = 0–11, number indicates at.%) alloys is investigated and the relationship between the fracture toughness and the fractography is discussed by observing the fracture morphology and analyzing the propagation of the crack. The micro-Vickers hardness results indicate that the hardness increases with increasing Fe content. The fracture toughness results indicate that Fe doping has improved the toughness of Ni–Mn–Ga alloys, and the toughness increases with increasing Fe content in Ni48.7Mn30.1−xFexGa21.2 (x = 0–11) alloys. Fracture morphology shows typical intergranular fracture with rock candy pattern in the Ni48.7Mn30.1Ga21.2 (x = 0) and river pattern cleavage fracture facets in the Ni48.7Mn19.1Fe11Ga21.2 (x = 11) alloy. The fracture type changing from intergranular fracture to transgranular fracture is the main reason for the improved toughness of Ni–Mn–Ga alloys by addition of Fe.

Effect of Fe content on fracture behavior of Ni–Mn–Fe–Ga ferromagnetic shape memory alloys

A series of biodegradable poly(L-lactide-co-ϵ-caprolactone) (PCLA) copolymers with different chemical compositions are synthesized and characterized. The mechanical properties and shape-memory behaviors of PCLA copolymers are studied. The mechanical properties are significantly affected by the copolymer compositions. With the ϵ-caprolactone (ϵ-CL) content increasing, the tensile strength of copolymers decreases linearly and the elongation at break increases gradually. By means of adjusting the compositions, the copolymers exhibit excellent shape-memory effects with shape-recovery and shape-retention rate exceeding 95%. The effects of composition, deformation strain, and the stretching conditions on the recovery stress are also investigated systematically. A maximum recovery stress around 6.2 MPa can be obtained at stretching at Tg − 15°C to 200% deformation strain for the PCLA70 copolymer. The degradation results show that the copolymers with higher ϵ-CL content have faster degradation rates and shape-recovery rates, meanwhile, the recovery stress can maintain a relative high value after 30 days in vitro degradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Shape-memory behaviors of biodegradable poly(L-lactide-co-ε-caprolactone) copolymers

Martensitic transformation and mechanical properties of Ni–Mn–Ga–Y ferromagnetic shape memory alloys

The thermal properties, crystalline structure and shape memory effects of poly(L-lactide) (PLLA) and poly(L-lactide-co-epsilon-caprolactone) (PCLA) copolymers are systematically investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and tensile tests. The effects of the deformation strain on the shape recovery rate and recovery stress are also revealed. The polymers have the PLLA crystal and the amorphous phase, which are served as the fixed phase and reversible phase, respectively. The shape recovery rate and the recovery stress are significantly affected by the compositions and the deformation strain. With the increase of the deformation strain, the shape recovery rate decrease and higher shape recovery rate can be obtained in the polymers which have higher epsilon-CL content. However, the variation of recovery stress with the deformation strain is quite different and the maximum recovery stress of all polymers exceeds 3 MPa.

Study on the shape memory effects of poly(l-lactide-co-ε-caprolactone) biodegradable polymers

Ni–Mn–In alloys are doped by Fe in order to improve the ductility of this intermetallic. The phase transformation behavior, microstructures and mechanical properties of Ni 50 Mn 34 In 16 −  y Fe y ( y  = 0, 2, 3, 4, 5, 8) alloys are investigated in this paper. The phase transformation temperatures increase with the increase of Fe content, and some second phase particles appear both along the grain boundaries and inside the grains after being doped 5 at.% and 8 at.% Fe. The compressive strength and maximum compressive strain reach up to 1200 MPa and 15.8% for amounts higher than 8 at.% Fe. In addition, the fracture type changes from typical intergranular crack to transgranular crack gradually with the increase of Fe content.

Z.Y. Gao

Papers

Effect of Fe content on fracture behavior of Ni–Mn–Fe–Ga ferromagnetic shape memory alloys

Shape-memory behaviors of biodegradable poly(L-lactide-co-ε-caprolactone) copolymers

Martensitic transformation and mechanical properties of Ni–Mn–Ga–Y ferromagnetic shape memory alloys

Study on the shape memory effects of poly(l-lactide-co-ε-caprolactone) biodegradable polymers

Investigation on martensitic transformation behavior, microstructures and mechanical properties of Fe-doped Ni–Mn–In alloys