Co-reporter:Ke Du and Zhihua Gan
Journal of Materials Chemistry A 2014 vol. 2(Issue 21) pp:3340-3348
Publication Date(Web):12 Mar 2014
DOI:10.1039/C3TB21861A
The shape memory properties of hydroxyapatite-graft-poly(D,L-lactide) (HA-g-PDLLA) nanocomposites were investigated in the present study. Hybrid nanocomposites with various HA proportions (5, 10, 15 and 25 wt%) were prepared via in situ grafting polymerization. It is found that the nanocomposites exhibit various shape memory (SM) performances with different HA loadings. Excellent shape memory properties were found for HA-g-PDLLA nanocomposites with 15 wt% inorganic HA proportions, observed through a well-established four-step SM programming cycle method. However, at low HA loading (including pure PDLLA), the samples experienced a severe relaxation process, which caused a plastic, irreversible deformation of the sample and resulted in a poor SM recovery ratio. In addition, the shape memory behaviours of HA25-g-PDLLA nanocomposites and HA25/PDLLA blends were compared. Due to the serious relaxation process caused by the weak interaction forces of hydrogen bonding between HA and PDLLA, the HA25/PDLLA blends had much worse shape recovery ability than the HA25-g-PDLLA nanocomposites.
Co-reporter:Junjie Liu
Macromolecular Bioscience 2014 Volume 14( Issue 5) pp:699-708
Publication Date(Web):
DOI:10.1002/mabi.201300488
Abstract
Amphiphilic diblock copolymers poly(ϵ-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) with well-controlled pendant azido groups along the hydrophilic PEO block, that is, poly(ϵ-caprolactone)-b-poly(ethylene oxide-co-glycidyl azide) (PCL-b-P(EO-co-GA)), are synthesized from poly(ϵ-caprolactone)-b-poly(ethylene oxide-co-epichlorohydrin) (PCL-b-P(EO-co-ECH)). The further conversion of those azido groups along the hydrophilic block of copolymers into amino or carboxyl groups via click chemistry is studied. The micelles self-assembled from PCL-b-P(EO-co-GA) with azido groups on the shell are crosslinked by the dialkynyl-PEO. The micelles with crosslinked shell show better stability, higher drug loading capacities, subsequent faster drug release rate, and higher cytotoxicity to cancer cells. The introduction of azido groups into PCL-b-PEO amphiphilic diblock copolymers from epichlorohydrin in PEO hydrophilic block in this work provides a new method for biofunctionalization of micelles via mild click chemistry.
Co-reporter:Danhua Zhou, Guan Zhang, Zhihua Gan
Journal of Controlled Release 2013 Volume 169(Issue 3) pp:204-210
Publication Date(Web):10 August 2013
DOI:10.1016/j.jconrel.2013.01.025
The aim of this work was to develop a targeted drug delivery system with potentials for intravesical instilled chemotherapy of superficial bladder cancer. The amphiphilic diblock copolymer poly(ε-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) was first conjugated with the cyclic (Arginine–Glycine–Aspartic acid–d-Phenylalanine–Lysine) (c(RGDfK)) and fluorescein isothiocyannate (FITC) via the functional terminal groups of hydrophilic block, and then assembled into micelles. The interaction between micelles and various model cells was well studied by means of confocal laser scanning microscopy and flow cytometry. The c(RGDfK) on the surface of the micelle was confirmed by 1H NMR analysis and cell affinity with human glioblastoma–astrocytoma cells (U87MG). The cell viability of bladder cancer cells (T-24 cells) after incubation with doxorubicin (DOX) loaded polymeric micelles was evaluated by in vitro cytotoxicity assay. The results revealed that c(RGDfK) modified micelles showed strong affinity to T-24 cells and strong inhibitory effect on the proliferation of T-24 cells when doxorubicin drug was loaded, indicating the high affinity of c(RGDfK) to bladder cancer cells. The c(RGDfK) modified micelles assembled from PCL-b-PEO diblock copolymers developed in this study are of great potentials as nano-scaled drug delivery system for intravesical instilled chemotherapy of superficial bladder cancer.
Co-reporter:Ke Du, Xudong Shi, and Zhihua Gan
Langmuir 2013 Volume 29(Issue 49) pp:15293-15301
Publication Date(Web):2017-2-22
DOI:10.1021/la404209u
Hydroxyapatite-graft-poly(d,l-lactide) (HA-g-PDLLA) nanoparticles were synthesized here to fabricate hybrid microspheres with diameter in the range of 150–200 μm by emulsion solvent evaporation techniques. The as-obtained microspheres were treated with alkaline solution in order to selectively degrade the PDLLA layer which covered on the surface of hybrid microspheres and instead to generate a dense coating of HA nanoparticles. The hybrid microspheres with enriched HA nanoparticles on the surface were further immersed in simulated body fluid (SBF) solution to evaluate the bone-forming ability of the bioactive hybrid microspheres via the in vitro biomimetic mineralization process. The resultant microspheres were analyzed by using X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) to understand the nucleation and growth of bioactive calcium phosphate (Ca–P) crystals as a function of surface treatment. Results in this work clearly demonstrated that the existing HA nanoparticles on the surface of hybrid microspheres after alkaline treatment greatly affect the growth of the bone-like Ca–P crystals in SBF solutions. The biomimetic hybrid microspheres were found to be excellent candidates for use as injectable scaffolds for bone tissue engineering.
Co-reporter:Dan-hua Zhou;Jie Zhang 张杰;Guan Zhang
Chinese Journal of Polymer Science 2013 Volume 31( Issue 9) pp:1299-1309
Publication Date(Web):2013 September
DOI:10.1007/s10118-013-1332-6
This work focuses on the interaction between polymeric micelles with different charged surfaces and cancer cells in order to study the influence of surface charge on the in vitro cellular uptake efficiency. The amphiphilic diblock copolymers poly(ɛ-caprolactone)-b-poly(ethylene oxide) (PCL-b-PEO) with different functional groups at the end of hydrophilic block were synthesized. The functional groups endue the micelles with different charges on the surfaces. The cellular uptake of micelles to T-24 cells (human bladder tumor cells), HepG2 cells (human liver hepatocellular carcinoma cell line) and Hela cells (human epithelial cervical cancer cells) was studied by means of flow cytometer and confocal laser scanning microscopy. The results indicate that the surface charges showed great influence on zeta potential of micelles at different pH values. The in vitro cellular uptake efficiency of micelles with different charged surfaces demonstrated different cellular uptake patterns to three kinds of cancer cells.
Co-reporter:Ke Du and Zhihua Gan
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 9) pp:4643
Publication Date(Web):August 8, 2012
DOI:10.1021/am301013e
A double template method to fabricate poly(ε-caprolactone) (PCL) hierarchical patterned nanowires with highly ordered nano- and microscaled topography was developed in this study. The topography of PCL film with a patterned nanowire surface can be easily and well controlled by changing the template and melting time of PCL film on the templates. The surface morphology, water contact angle, protein adsorption, and cell growth behavior on the PCL films with different surface structures were well studied. The results revealed that the PCL nanowire arrays and the hierarchical patterned nanowires showed higher capability of protein adsorption and better cell growth than the PCL film with smooth surface. Typically, the PCL surface with hierarchical nanowire patterns was most favorable for cell attachment and proliferation. The present study was innovative at fabrication of polymer substrates with hierarchical architecture of nanowires inside microscaled islands to gain insight into the cell response to this unique topography and to develop a new method of constructing the bionic surface for tissue engineering applications.Keywords: cell adhesion; double template; patterned nanowires; poly(ε-caprolactone); protein adsorption; topography;
Co-reporter:Zhenke Wei;Qingsong Yu
Macromolecular Research 2012 Volume 20( Issue 3) pp:313-318
Publication Date(Web):2012 March
DOI:10.1007/s13233-012-0060-z
Co-reporter:Zhenke Wei;Xiaojuan Hao;Timothy C. Hughes
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 12) pp:2378-2388
Publication Date(Web):
DOI:10.1002/pola.26012
Abstract
Soluble hyperbranched glycopolymers were prepared by copolymerization of glycan monomers with reversible addition-fragmentation chain transfer polymerization (RAFT) inimers in a simple one-pot reaction. Two novel RAFT inimers, 2-(methacryloyloxy)ethyl 4-cyano-4-(phenylcarbonothioylthio)pentanoate (MAE-CPP) and 2-(3-(benzylthiocarbonothioylthio)propanoyloxy)ethyl acrylate (BCP-EA) were synthesized and used to prepare hyperbranched glycopolymers. Two types of galactose-based saccharide monomers, 6-O-methacryloyl-1,2:3,4-di-O-isopropylidene-D-galactopyranose (proGal-M) and 6-O-(2′-acrylamido-2′-methylpropanoate)-1,2:3,4-di-O-isopropylidene-D-galactopyranose (proGal-A), containing a methacrylate and an acrylamide group, respectively, were also synthesized and polymerized under the mediation of the MAE-CPP and BCP-EA inimers, respectively. In addition, hyperbranched poly(proGal-M), linear poly(proGal-A), and hyperbranched poly(proGal-A) were generated and their polymerization kinetics were studied and compared. An unexpected difference was observed in the kinetics between the two monomers during polymerization: the relationship between polymerization rate and concentration of inimer was totally opposite in the two monomer–inimer systems. Branching analysis was conducted by using degree of branching (DB) as the measurement parameter. As expected, a higher DB occurred with increased inimer content. Furthermore, these polymers were readily deprotected by hydrolysis in trifluoroacetic acid solution resulting in water-soluble polymers. The resulting branched glycopolymers have potential as biomimetics of polysaccharides. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Zhenke Wei, Xiaojuan Hao, Peter A. Kambouris, Zhihua Gan, Timothy C. Hughes
Polymer 2012 Volume 53(Issue 7) pp:1429-1436
Publication Date(Web):22 March 2012
DOI:10.1016/j.polymer.2012.02.011
Two novel RAFT inimers, small molecule inimer 2-(methacryloyloxy)ethyl 4-cyano-4-(phenylcarbonothioylthio)pentanoate (MAE-CPP) and macro inimer PMMA-MAE-CPP were synthesized and used to prepare hyperbranched polymers via RAFT polymerization without the use of a divinyl cross-linker. The hyperbranched polymers synthesized included copolymers of MAE-CPP with styrene, copolymers of the macro inimer PMMA-MAE-CPP with styrene and the homopolymerization product of the macro inimer PMMA-MAE-CPP. The spectroscopic characteristics and polymerization kinetics of these RAFT polymers obtained under different polymerization conditions were systematically studied and the results compared with those obtained from the corresponding linear RAFT polymerizations as well as from hyperbranched polymerizations performed in the presence of a divinyl cross-linker which are reported in literature. The RAFT methodology reported here for the preparation of hyperbranched polymers is simpler than those reported previously using a divinyl cross-linker and provides good control over the hyperbranched polymers without the formation of insoluble gels.
Co-reporter:Yu Zhang;Ni Jiang
Science China Chemistry 2011 Volume 54( Issue 2) pp:369-374
Publication Date(Web):2011 February
DOI:10.1007/s11426-010-4214-6
In situ evaluation of cell cultivation on degrading poly(ɛ-caprolactone) (PCL) films was studied. New culture surroundings were constructed for cell growth by using PCL films as substrates and adding Pseudomonas cepacia lipase to accelerate biodegradation of PCL films. MTT experiments for 10 h indicated the low cytotoxicity of lipase solution with concentration up to 0.2 mg/mL for MG-63 cells growth on PCL films. With the optimized lipase concentration and degradation time, we studied cell growth behavior on dynamically changed PCL films by adding lipase to the culture surroundings. MTT, fluorescence microscopy and scanning electron microscopy (SEM) were used to evaluate cell viability, proliferation and morphologies. It was found that cell viability and proliferation were not affected by the added lipase solution negatively. In contrast, cells cultured on degrading PCL films showed good growth behavior with clear fusiform shape and pseudopods. Importantly, the enzymatic degradation of PCL films with cells attachment showed distinctive morphology compared to the degradation in lipase solution without cells. The simultaneous cell growth and PCL film degradation were well discussed in this work, which may better understand the interaction between cell growth and polymer degradation.
Co-reporter:Xudong Shi, Jian Jiang, Lei Sun, Zhihua Gan
Colloids and Surfaces B: Biointerfaces 2011 Volume 85(Issue 1) pp:73-80
Publication Date(Web):15 June 2011
DOI:10.1016/j.colsurfb.2010.11.016
Poly(lactic acid) (PLA) microspheres have great potential in bone tissue engineering. However, their applications have been limited by surface and bulk properties such as hydrophobicity, lack of cell recognition sites and acidic degradation products. Apatite is a mineral which can effectively promote the adhesion and growth of bone cells. In this study, the bonelike mineral, carbonate apatite, was successfully used to functionalize porous PLA microspheres by a biomimetic mineralization method. To improve apatite formation, porous PLA microspheres were first selectively hydrolyzed in NaOH solution to increase the density of polar anionic groups on the surface, and then immersed in simulated body fluid for biomineralization. The morphology, composition, and phase structure of bioactive mineral grown on the original and hydrolyzed PLA microspheres were analyzed and compared quantitatively. The results showed that the hydrolysis which took place on the PLA microspheres enhanced the nucleation and growth of apatite. MG-63 cells attached well and spread actively on the mineralized PLA microspheres, indicating their strong potential in bone tissue engineering.Graphical abstractResearch highlights▶ Post hydrolysis is an efficient method to control the porous size of microspheres. ▶ Hydrolyzed PLA porous microspheres improve the biomineralization ability. ▶ Biomineralization promotes the adhesion and growth of bone cells on microspheres.
Co-reporter:Peijian Sun;Yu Zhang;Linqi Shi
Macromolecular Bioscience 2010 Volume 10( Issue 6) pp:621-631
Publication Date(Web):
DOI:10.1002/mabi.200900434
Co-reporter:Ni Jiang, Lifen Zhao, Zhihua Gan
Polymer Degradation and Stability 2010 Volume 95(Issue 6) pp:1045-1053
Publication Date(Web):June 2010
DOI:10.1016/j.polymdegradstab.2010.03.004
The effects of nucleating agent multimethyl-benzilidene sorbitol (TM6) on crystallization and morphology of poly(butylene adipate) (PBA) with polymorphic crystal structures were studied by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarized optical micrographs (POM). In addition to the heterogeneous nucleation, TM6 changes the formation conditions of PBA polymorphic crystals. The addition of TM6 is favorable for the formation of PBA α-form crystals, resulting in the morphological changes from spherulites to interpenetrated fibrils. The influences of TM6 on enzymatic degradation of PBA were studied in terms of the morphological change and weight loss. The results indicate that the α-form crystals induced by TM6 show much slower degradation rate. This work provides an efficient method to control the polymorphic crystal structure and further to regulate the biodegradation rate of polymer materials through modulating the homogeneous and heterogeneous nucleation modes by adding nucleating agents.
Co-reporter:Yu Zhang, Lei Sun, Jian Jiang, Xiaolin Zhang, Wenjun Ding, Zhihua Gan
Polymer Degradation and Stability 2010 Volume 95(Issue 8) pp:1356-1364
Publication Date(Web):August 2010
DOI:10.1016/j.polymdegradstab.2010.01.025
Biodegradable microspheres were fabricated by poly(ɛ-caprolactone) (PCL) homopolymer and poly(ɛ-caprolactone-b-ethylene oxide) (PCL-b-PEO) amphiphilic block copolymer. The regulation of microsphere surface morphology was successfully achieved by controlled enzymatic degradation. The morphological changes induced by biodegradation and their influences on the growth of MG-63 human osteosarcoma cells were studied. Results based on the evaluation of cytotoxicity and the morphological observation of MG-63 cells cultivated on microspheres showed better growth of cells on the surface of degraded microspheres than on the surface of those undegraded microspheres no matter they were fabricated by homopolymers or copolymers. The influences of morphological changes of microsphere surface before and after biodegradation on MG-63 cell growth were discussed. The results of this work indicated that the biodegradation-induced morphological changes of microspheres could be well controlled and were favorable for MG-63 cell attachment and proliferation.
Co-reporter:Yu Zhang;PeiJian Sun
Science China Chemistry 2010 Volume 53( Issue 3) pp:519-527
Publication Date(Web):2010 March
DOI:10.1007/s11426-010-0095-y
A series of controllable amphiphilic block copolymers composed of poly(ethylene oxide) (PEO) as the hydrophilic block and poly(ɛ-caprolactone) (PCL) as the hydrophobic block with the amino terminal group at the end of the PEO chain (PCL-b-PEO-NH2) were synthesized. Based on the further reaction of reactive amino groups, diblock copolymers with functional carboxyl groups (PCL-b-PEO-COOH) and functional compounds RGD (PCL-b-PEO-RGD) as well as the triblock copolymers with thermosensitive PNIPAAm blocks (PCL-b-PEO-b-PNIPAAM) were synthesized. The well-controlled structures of these copolymers with functional groups and blocks were characterized by gel permeation chromatography (GPC) and 1H NMR spectroscopy. These copolymers with functionalized hydrophilic blocks were fabricated into microspheres for the examination of biofunctions via cell culture experiments and in vitro drug release. The results indicated the significance of introducing functional groups (e.g., NH2, COOH and RGD) into the end of the hydrophilic block of amphiphilic block copolymers for biomedical potentials in tissue engineering and controlled drug release.
Co-reporter:Ni Jiang, Shidong Jiang, Yi Hou, Shouke Yan, Guangzhao Zhang, Zhihua Gan
Polymer 2010 Volume 51(Issue 11) pp:2426-2434
Publication Date(Web):14 May 2010
DOI:10.1016/j.polymer.2010.03.058
Solution-grown lamellar single crystals of PCL homopolymer and amphiphilic block copolymers of PCL-b-PEO-b-PCL and PCL-b-PEO-FG (functional groups FG = NH2, OCH3) were prepared by self-seeding procedures. The crystal structure and morphology of these single crystals were mainly studied by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). The results indicated that the shorter PEO blocks as well as the functional groups bonded to the end of PEO block are in an amorphous state and located in the surface of single crystals. The enzymatic degradation of single crystals prepared from these homopolymer and amphiphilic block copolymers has been well-studied to demonstrate the effects of chemical structure on degradation behavior. The single crystals showed similar morphologies before enzymatic degradation but very different surface character after enzymatic degradation. Such differences resulted from the PEO block and functional end groups. The results of this work indicated the important role of chemical structure in determining biodegradation behavior.
Co-reporter:Tianchang Wang, Haijun Wang, Huihui Li, Zhihua Gan and Shouke Yan
Physical Chemistry Chemical Physics 2009 vol. 11(Issue 10) pp:1619-1627
Publication Date(Web):21 Jan 2009
DOI:10.1039/B817597G
Banded spherulites of PEA, PBS and their PBS–PEA blends were studied by optical and atomic force microscopies. It was found that PEA forms a regular banded structure within the temperature range 23 °C to 36 °C, otherwise only Maltese-cross spherulites are observed. The banded PEA spherulites exhibit a double ring feature with band spacing between two equivalent birefringent rings increasing with temperature. The ring extinction in PEA banded spherulites is caused by a lamellar twist. There exist two equivalent positions in one twisting period, which show no birefringence. The PBS can also grow in ring-banded spherulites in a wide temperature window with the high temperature threshold for forming banded structures that are not sharply delineated, as in the case of PEA. Also the double ring feature is not so pronounced for the spherulites of pure PBS. Blending PBS with PEA is found to favor the formation of PBS banded structures. During the crystallization process, the early growing PBS spherulites at 75 °C show weak birefringence with an evident ring-banded structure. The crystallization of PEA at 0 °C makes a great contribution to the birefringence increment of the initially-birefringent rings. This is caused by the analogic crystal orientation of PBS and PEA based on interlamellar phase separation as revealed by AFM observation. The band spacing of PBS spherulites is found to be increase with both increasing temperature and increasing PEA content. This stems from an increment in chain mobility of PBS both with temperature and addition of the PEA component.
Co-reporter:Xudong Shi;Lei Sun;Jian Jiang;Xiaolin Zhang;Wenjun Ding
Macromolecular Bioscience 2009 Volume 9( Issue 12) pp:1211-1218
Publication Date(Web):
DOI:10.1002/mabi.200900224
Co-reporter:Jing Mao
Macromolecular Bioscience 2009 Volume 9( Issue 11) pp:1080-1089
Publication Date(Web):
DOI:10.1002/mabi.200900104
Co-reporter:Wenyuan Xie, Zhihua Gan
Polymer Degradation and Stability 2009 Volume 94(Issue 7) pp:1040-1046
Publication Date(Web):July 2009
DOI:10.1016/j.polymdegradstab.2009.04.005
Co-reporter:Wenyuan Xie;Ni Jiang
Macromolecular Bioscience 2008 Volume 8( Issue 8) pp:775-784
Publication Date(Web):
DOI:10.1002/mabi.200800011
Co-reporter:Guoqiang Yu;Yu Zhang;Xudong Shi;Zhanshuang Li
Journal of Biomedical Materials Research Part A 2008 Volume 84A( Issue 4) pp:926-939
Publication Date(Web):
DOI:10.1002/jbm.a.31325
Abstract
Microspheres fabricated by biodegradable polymers with tunable surface properties show great potentials as microcarriers in in vitro cell cultivation and tissue engineering. Herein we reported a new method to regulate the surface property and morphology of microspheres via the synthesis of biodegradable amphiphilic block copolymers with adjustable compositions. The poly(ϵ-caprolactone-b-ethylene oxide) diblock copolymers with functional amino end groups bonding to the PEO block (PCL-b-PEO-NH2) were synthesized by sequential ring-opening polymerization with potassium bis(trimethylsilyl) amide as initiator. The copolymers were characterized by gel permeation chromatography (GPC) and 1H NMR, and then used to fabricate microspheres by w/o/w double emulsion solvent evaporation technique. The surface properties of microspheres were studied by means of scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results indicated that both the fabrication conditions and copolymer composition have great influences on the surface morphology and property of microspheres. The reactive amino functional groups are dominantly located on the surface of microspheres. The in vitro degradation of microspheres was studied by following the morphological changes of microspheres. The influences of hydrophilic PEO out-layers on the enzymatic degradation of microspheres were discussed. These microspheres with controllable surface morphology and amino functional groups are expected to be promising alternatives for the further biomimetic modification to promote cell growth on materials. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Co-reporter:Xudong Shi, Zhihua Gan
European Polymer Journal 2007 Volume 43(Issue 12) pp:4852-4858
Publication Date(Web):December 2007
DOI:10.1016/j.eurpolymj.2007.09.024
Poly(propylene carbonate) (PPC) is a new biodegradable aliphatic polycarbonate. However, the poor thermal stability and low glass transition temperatures (Tg) have limited its applications. To improve the thermal properties of PPC, organophilic montmorillonite (OMMT) was mixed with PPC by a solution intercalation method to produce nanocomposites. An intercalated-and-flocculated structure of PPC/OMMT nanocomposites was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal and mechanical properties of PPC/OMMT nanocomposites were investigated by thermal gravimetric analysis (TGA), differential scanning calorimetric (DSC), and electronic tensile tester. Due to the nanometer-sized dispersion of layered silicate in polymer matrix, PPC/OMMT nanocomposites exhibit improved thermal and mechanical properties than pure PPC. When the OMMT content is 4 wt%, the PPC/OMMT nanocomposite shows the best thermal and mechanical properties. These results indicate that nanocomposition is an efficient and convenient method to improve the properties of PPC.
Co-reporter:Lifen Zhao, Zhihua Gan
Polymer Degradation and Stability 2006 Volume 91(Issue 10) pp:2429-2436
Publication Date(Web):October 2006
DOI:10.1016/j.polymdegradstab.2006.03.012
The introduction of aromatic butylene terephthalate (BT) units into the backbone chains of aliphatic poly(butylene adipate) (PBA) not only changes the mechanical performance of the resultant P(BA-co-BT) copolymers but also affects their biodegradability. Because of the polymorphism of PBA homopolymer, the copolymerized BT units may also influence the polymorphic crystal structure as well as the biodegradation behavior. In this work, three P(BA-co-BT) copolymers with BT contents as 10, 20, and 25 mol% were chosen to study their polymorphic crystal structure, thermal properties and enzymatic degradation by means of wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and gravimetric methods. The results reveal that the P(BA-co-BT) copolymers with BT contents below 25 mol% can form polymorphic crystal structures after melt-crystallization at different temperatures. However, the recrystallization and transformation of polymorphic crystals are strongly affected by the rigid BT units. The enzymatic degradation rates of P(BA-co-BT) copolymers decrease with increasing the BT contents. The influences of the BT units on the polymorphism and enzymatic degradation are discussed in terms of the motion of PBA chains that copolymerized with BT units. It has been concluded from the examination of solid-state microstructure that the influence of the aromatic BT units on the motion of biodegradable PBA chains heavily influences the biodegradability.
Co-reporter:Zhihua Gan, Kazuhiro Kuwabara, Hideki Abe, Tadahisa Iwata, Yoshiharu Doi
Polymer Degradation and Stability 2005 Volume 87(Issue 1) pp:191-199
Publication Date(Web):January 2005
DOI:10.1016/j.polymdegradstab.2004.08.007
The enzymatic degradation of melt-crystallized poly(butylene adipate) (PBA) films corresponding to the α crystal structure, β crystal structure, and the two mixed crystal forms were studied by using the lipase from Pseudomonas sp. The results indicate that the degradation of each crystal form depends on its crystal size, while the comparison of degradation between polymorphic crystals indicates that there is no relationship between thermodynamic stability and biodegradability. The films with α crystal structure were found to have faster degradation rate than the films with β crystal structures, although the α crystal is a thermodynamically stable phase with larger crystal size. The films with mixed α and β crystal structures showed a lowest degradation rate. In order to study the degradation mechanism, the morphologies of melt-crystallized PBA films before and after enzymatic degradation were studied by means of polarized optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Different spherulite morphologies have been found in the PBA films corresponding to the different crystal structures. The PBA films with mixed α and β crystal structures showed spherulites with banded rings, while the films with either α or β crystal structure did not show banded spherulites. In addition, the oriented “lines” which are crystalline structures induced by the Teflon films during melt-crystallization were only observed on the film surface with α crystal structure. The influences of surface structure, morphology, and chain mobility of polymorphic crystals were discussed for understanding the role of crystal structure and morphology in determining the biodegradability of polymorphic crystals.
Co-reporter:Ke Du and Zhihua Gan
Journal of Materials Chemistry A 2014 - vol. 2(Issue 21) pp:NaN3348-3348
Publication Date(Web):2014/03/12
DOI:10.1039/C3TB21861A
The shape memory properties of hydroxyapatite-graft-poly(D,L-lactide) (HA-g-PDLLA) nanocomposites were investigated in the present study. Hybrid nanocomposites with various HA proportions (5, 10, 15 and 25 wt%) were prepared via in situ grafting polymerization. It is found that the nanocomposites exhibit various shape memory (SM) performances with different HA loadings. Excellent shape memory properties were found for HA-g-PDLLA nanocomposites with 15 wt% inorganic HA proportions, observed through a well-established four-step SM programming cycle method. However, at low HA loading (including pure PDLLA), the samples experienced a severe relaxation process, which caused a plastic, irreversible deformation of the sample and resulted in a poor SM recovery ratio. In addition, the shape memory behaviours of HA25-g-PDLLA nanocomposites and HA25/PDLLA blends were compared. Due to the serious relaxation process caused by the weak interaction forces of hydrogen bonding between HA and PDLLA, the HA25/PDLLA blends had much worse shape recovery ability than the HA25-g-PDLLA nanocomposites.
Co-reporter:Tianchang Wang, Haijun Wang, Huihui Li, Zhihua Gan and Shouke Yan
Physical Chemistry Chemical Physics 2009 - vol. 11(Issue 10) pp:NaN1627-1627
Publication Date(Web):2009/01/21
DOI:10.1039/B817597G
Banded spherulites of PEA, PBS and their PBS–PEA blends were studied by optical and atomic force microscopies. It was found that PEA forms a regular banded structure within the temperature range 23 °C to 36 °C, otherwise only Maltese-cross spherulites are observed. The banded PEA spherulites exhibit a double ring feature with band spacing between two equivalent birefringent rings increasing with temperature. The ring extinction in PEA banded spherulites is caused by a lamellar twist. There exist two equivalent positions in one twisting period, which show no birefringence. The PBS can also grow in ring-banded spherulites in a wide temperature window with the high temperature threshold for forming banded structures that are not sharply delineated, as in the case of PEA. Also the double ring feature is not so pronounced for the spherulites of pure PBS. Blending PBS with PEA is found to favor the formation of PBS banded structures. During the crystallization process, the early growing PBS spherulites at 75 °C show weak birefringence with an evident ring-banded structure. The crystallization of PEA at 0 °C makes a great contribution to the birefringence increment of the initially-birefringent rings. This is caused by the analogic crystal orientation of PBS and PEA based on interlamellar phase separation as revealed by AFM observation. The band spacing of PBS spherulites is found to be increase with both increasing temperature and increasing PEA content. This stems from an increment in chain mobility of PBS both with temperature and addition of the PEA component.
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2.png)
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2_b.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4_b.png)