Poly (L-lactide-co-e-caprolactone)/Functionalized CNTs Nanocomposite,Thermal and Mechanical Properties

Multiwalled carbon nanotubes(MWCNTs) grafted with poly(L-lactide-e-caprolactone)(PCLA) were synthesized by ring opening polymerization reaction and used as a reinforcement for neat PCLA.Scanning electron microscopy(SEM) revealed that the applied tensile load on the composite was transferred to the MWNT-OH-g-PCLA,loading to a strain failure of the MWCNTs rather than an adhesive failure between the MWCNTs and the matrix.

Ring-opening Polymerization ofε-Caprolactone Using Lanthanide Tris(4-tert-butylphenolate)s as a Single-component Initiator

The ring-opening polymerization of e-caprolactone (CL) initiated by novel single lanthanide tris(4-tert-butylphenolate)s [Ln(OTBP)3] is reported. Single-component La(OTBP)3 can effectively prepare polycaprolactone (PCL) with over 90% yield and viscosity average molecular weight about 60 x 10 under quite mild conditions: molar ratio of CL to initiator is 1000, 60 C, 2 h in toluene. Mechanism study indicates that the monomer inserts into the growing chain via the break of acyl-oxygen bond of CL.

Microwave-assisted Polymerization of ε-Caprolactone with Maleic Acid as Initiator and Drug Release Behavior of Ibuprofen-Poly(ε-caprolactone) System

Poly(e-caprolactone) (PCL) with weight-average molar mass over 10000 g/mol was synthesized by microwave-assisted ring-opening polymerization of e-caprolactone (e-CL) with maleic acid (MA) as initiator (2.45 GHz, 360 W, 85 min). Ibuprofen-PCL controlled release system was prepared directly by the ROP of e-CL in its mixture with ibuprofen. The release of ibuprofen from the system was sustained and steady.

Synthesis and Characterization of a Zwitterionic Copolymer Poly (ε-caprolactone)-b-poly(carboxybetaine methacrylate) with Good Cell Affinity

Design of polymeric scaffolds with specific physical and biological properties is a key objective of tissue engineering research. In this work, a novel copolymer poly （e-caprolactone）-b-poly （carboxybetaine methacrylate） （PCL-PCBMA） containing zwitterion and polyester segments, was synthesized through ATRP technique. The chemical structure, composition,and molecular weight of the synthesized copolymer were characterized by ~HNMR and GPC. The polymer was further electrospun into fibrous film which has been characterized by SEM, XPS, water uptake test, and MTT cell culture assay. All these results indicate that this kind of copolymer is a suitable candidate for the application in vascular tissue engineering.

The antibacterial and drug-loaded bilayer poly(c-caprolactone) fibrous membrane with a shish-kebab structure

Electrospinning has been widely used in the field of biomedical materials characterized with high porosity and good breathability as well as similarity to the natural extracellular matrix.This study employs the microsol-electrospinning technology combined with the self-induced crystallization method to fabricate the functionalized bilayer poly(e-caprolactone)(PCL)fibrous membrane with a shish-kebab(SK)structure.The outer layer consists of the antibacterial SK-structured fibrous membrane showing favorable mechanical properties and notable inhibitory effects on the growth of E.coli and S.aureus,while salvianic acid A sodium(SAs)is encapsulated in the inner core shell and SK-structured PCL fibrous membrane,achieving the controlled and sustained release of SAs.Moreover,good biocompatibility and enhanced cell adhesion of this membrane are also revealed.This antibacterial and drug-loaded bilayer PCL fibrous membrane with a Sk structure demonstrates superior mechanical characte-ristics,exceptional antibacterial properties,and notable biocompatibility,suggesting its favorable outlook for future development in the area of tissue engineering.

SELF-HEALING BIODEGRADABLE POLY(UREA-URETHANE) ELASTOMERS BASED ON HYDROGEN BONDING INTERACTIONS

Self-healing poly（urea-urethane）s （PUUs） showing a tolerance to mechanical damage are particularly desirable for high-performance elastomeric biomaterials. In this study a kind of biodegradable PUUs was synthesized from poly（e-caprolactone） diol with L-lysine ethyl ester diisocyanate （LDI） extended with L-lysine ethyl ester dihydrochloride （LEED） in DMF and characterized by using 1H-NMR, FTIR, DSC, XRD, SEM and tensile tests. Interestingly, they exhibited a self-healing characteristic upon exposure to 37℃ for as short as 30 min with the tensile strength keeping at 4.23 MPa and the elongation at break reaching to 627%. It is revealed that increasing the hard segment content in PUUs benefits the self-healing performance, and on the opposite increasing the soft segment content contributes to the biodegradability.

Development of L-arginine-based poly(ester urethane)urea for enhanced vascular adaptability

Mismatched biomechanical properties between artificial vascular grafts and native blood vessels can result in intimal hyperplasia,especially for the implantation of small-diameter blood vessels.Ideal biomaterials for vascular repair still remain challenged.Biodegradable poly(ε-caprolactone)(PCL)has been applied for the preparation of electrospun vascular grafts,but more efforts are needed to improve its compliance with tissue growth.Herein,L-arginine-based poly(ester urethane)urea(PEUU)with both elasticity and biodegradability was synthesized so as to enhance the biomechanical properties of vascular grafts by blending electrospinning with PCL in a given mass ratio.It was exhibited that the prepared electrospun PCL/PEUU fibrous membranes were suitable for cell proliferation with normal cell morphology.More importantly,the electrospun membrane with 1/1 mass ratio of PCL/PEUU(PEUU50)showed specific flexibility,exhibiting more suitable mechanical properties matching to the native blood vessels.Specifically,the PEUU50 electrospun membrane demonstrated significantly lower Young’s modulus(9.3±0.8 MPa)and tensile strength(6.0±0.5 MPa),and extremely higher elongation(389%±24%)in wet state than those(16.3±3.0 MPa,11.4±7.1 MPa and 196%±57%,respectively)of the pristine PCL membrane.Overall,this study demonstrated the great potential of amino acid-based PEUUs for the application in small-diameter vascular grafts.

Observation of banded spherulites and lamellar structures by atomic force microscopy

Lamellar structures of banded spherulites of poly(e-caprolactone)/poly(vinylchloride) (PCL/PVC) blends are observed using tapping mode atomic force microscopy (AFM). Thesurface of the PCL/PVC banded spherulites presents to be concentric periodic ups and downs. Theperiod of the bands corresponds to the extinction rings under the polarized optical microscopyobservation. The lamellae with edge-on orientation in the ridges and the flat-on lamellae in thevalleys of the banded spherulites are observed clearly. The twisting between the edge-on and flat-onlamellae is also observed.

RING-OPENING POLYMERIZAION OF 2,2-DIMETHYLTRIMETHYLENE CARBONATE INITIATED BY INSITU GENERATED,TETRAHYDROSALEN STABLIZED YTTRIUM BOROHYDRIDE COMPLEX AND RANDOM COPOLYMERIZATION WITH ε-CAPROLACTONE

The poly（2,2-dimethyltrimethylene carbonate） （PDTC） with one hydroxyl and one formate terminal functions was synthesized by in situ generated, tetrahydrosalen stabilized yttrium borohydride complex. The influences of monomer/initiator molar ratio, temperature and reaction time on polymerization of DTC were investigated. Under the condition： [DTC]/[I] = 500, 55℃, toluene： 0.5 mL, DTC： 0.6 g, PDTC with Mn = 15600 and PDI = 2.15 was obtained. Through 1H-NMR and 13C-NMR analyses, the structure of PDTC was characterized and a coordination-insertion mechanism was proposed. In addition, the random copolymerization of DTC and caprolactone （CL） initiated by rare-earth borohydride compound was studied. The microstructure of PDTC-co-PCL includes four diads： DTC-CL, CL-CL, DTC-DTC and CL- DTC, which were determined by the specific signals in lH-NMR spectra. Based on the typical signals of the formate （δ = 8.08） and hydroxyl （δ= 3.34） end groups of PDTC-co-PCL, a mechanism involving DTC monomer inserts before CL during the initiation process was presumed. Furthermore, the thermal properties of amorphous copolymer were characterized by differential scanning calorimetry （DSC）. The results support the random structure of PDTC-co-PCL.