The effect of filler content on mechanical properties and cell response of elastomeric PGS/apatite foam scaffolds

Poly(glycerol sebacate) (PGS) is a novel polymeric material intended for applications in tissue engineering (TE). This study involves synthesizing the PGS prepolymer (pPGS) and subsequent manufacturing of porous PGS-based scaffolds with an addition of hydroxyapatite (HAp) by means of thermally induced phase separation followed by thermal cross-linking and salt-leaching (TIPS-TCL-SL). The study aims to investigate the effect of the apatite filler content on properties and morphology of porous PGS/HAp scaffolds. The emphasis is put on the mechanical behavior of the material characterized by means of compression tests and dynamic thermal mechanical analysis (DMTA). In addition to the reference polymer scaffold, the composites with filler contents of 10, 20 and 30 wt% have been examined. Our research revealed that the HAp content does not affect the mechanical properties in a directly proportional manner. The 30 wt% addition of HAp resulted in frayed structure and decrease in the mechanical parameters in comparison to other tested specimens. On the other hand, an addition of 10% did not sufficiently boost the properties. Therefore, a 20% addition of HAp was concluded to have superior mechanical properties in comparison to other analyzed specimens. A similar relationship results from the DMTA studies. Moreover, the strain sweep and frequency sweep tests confirmed the stability of the mechanical parameters in various conditions, as well as the elastomeric nature of the materials. Finally, the material did not exhibit cytotoxicity against standard L929 fibroblasts and cells readily populated the scaffolds.     

Synthesis,characterization and properties of biocompatible poly(glycerol sebacate) pre‐polymer and gel

Poly(glycerol sebacate) (PGS) is an elastomer with potential biomedical applications but it suffers from problems with irreproducible synthesis and the unacceptable toxicity of very soft PGS elastomers. To establish the reason for these problems, PGS was synthesized using different temperatures and reaction times, and the reaction was monitored by titration of the unreacted carboxylic groups and measurement of the mass loss during synthesis. It was found that evaporation of glycerol was a major cause of irreproducibility of the elastomer synthesis and this was more significant at higher reaction temperatures. The polymer microstructure was analysed using NMR spectroscopy and all twelve acylglyceride ¹³C‐signals as well as two small extra peaks of the residual glycerol were observed for the pre‐polymer. For the PGS gel, the glyceride moieties were characterized using NMR spectroscopy for the first time. The modulus and ultimate tensile strength of the gel increased with longer cure times and at higher cure temperatures while the elongation to break decreased and this was interpreted in terms of network theory. The cell viability of mouse fibroblasts was better for PGS samples with a higher conversion.© 2012 Society of Chemical Industry     

Controlled release of fluorouracil (5-FU) from chitosan-co-poly(ethylene glycol)/ poly(glycerol sebacate)-co-poly(ethylene glycol)-coated iron oxide

A blend of polyglycerol sebacate-poly ethylene glygol/chitosan-poly ethylene glycol-coated iron oxide (PGS-PEG/CS-PEG@Fe₃O₄) nanoparticles for 5FU delivery was prepared by reverse ultrasonic emulsification method. To enhance polymers’ solubility, PEG was grafted. Chemical characterization was performed through Fourier transformed infrared and proton nuclear magnetic resonance spectra. In vitro assay revealed that release profile of 5FU-loaded PGS-PEG/CS-PEG@Fe₃O₄ is sustained. Moreover, cytotoxicity was analyzed on HT29 cell line at the presence of external magnetic field using the lactate dehydrogenase and Alamar Blue. Results illustrate that (PGS-PEG/CS-PEG@Fe₃O₄) is promising to use as a carrier for 5FU anticancer agent with sustained tailored release.     

Synthesis and characterization of adamantane-containing poly(enaminonitriles)

The first aliphatic bis(chlorovinylidene cyanide) monomer, 1,3-bis(1-chloro-2,2-dicyanovinyl)adamantane, has been synthesized and polymerized with appropriate diamines to give adamantane-containing aromatic-aliphatic and all aliphatic poly(enaminonitriles) (PEANs) via vinylic nucleophilic substitution polymerization. The PEANs showed excellent solubility in polar aprotic solvents and good thermal stability (10% weight loss in air > 320 °C), despite the aliphatic contents of the polymers. Solution inherent viscosities of 0.23-0.90 dL/g were obtained.Three other new PEANs containing the adamantane-based cardo group were also synthesized via vinylic nucleophilic substitution polymerization from the adamanaine-containing cardo diamine 2,2-bis[4-(4-aminophenoxy)phenyl]adamantane. The cardo PEANs showed better solubility in common organic solvents than the corresponding cardo polyamides. They also showed good thermal stabilities (10% weight loss in air > 339 °C) comparable to those of the corresponding cardo polyamides.     

Synthesis and properties of poly(ferrocenylsilane) high polymers

Ring-opening polymerization of strained, ring-tilted cyclic ferrocenylsilanes has recently provided access to the first examples of high molecular weight poly(ferrocenylsilanes) [1], which possess backbones of alternating ferrocenyl groups and silicon atoms. In this paper we provide an overview of the progress to date on the synthesis and properties of these unusual polymers.Presented at the XXVIth Silicon Symposium, Indiana University-Purdue University at Indianapolis, March 26–27, 1993.     

Synthesis and properties of polymer brush consisting of poly(phenylacetylene) main chain and poly(dimethylsiloxane) side chains

A novel polymer brush consisting of poly(phenylacetylene) (PPA) main chain and poly(dimethylsiloxane) (PDMS) side chains was synthesized by the polymerization of phenylacetylene-terminated PDMS macromonomer (M-PDMS). The macromonomer was prepared by the esterfication of monohydroxy-ended PDMS (PDMS-OH, degree of polymerization (DP) = 42) with p-ethynylbenzoic acid. The polymerization of M-PDMS using [(nbd)RhCl]₂/Et₃N catalyst led to polymer brush, poly(M-PDMS), with M_n up to 349?000 (DP of main chain 104). Poly(M-PDMS) with narrow molecular weight distribution (M_n = 39?900, M_w/M_n = 1.11) was obtained with a vinyl-Rh catalyst, [Rh{C(Ph)CPh₂}(nbd){P(4-FC₆H₄)₃}]/(4-FC₆H₄)₃P. Poly(M-PDMS)s were brown to orange viscous liquids and soluble in organic solvents such as toluene and CHCl₃. The UV-vis absorptions of poly(M-PDMS) were observed in the range of 350-525 nm, which are attributable to the PPA main chain.     

Synthesis, characterization, and properties of poly(ethylene terephthalate)/poly(1,4-butylene succinate) block copolymers

Reactive blending at 290 °C of a series of mixtures of poly(ethylene terephthalate) (PET) and poly(1,4-butylene succinate) (PBS) led to the formation of block PET/PBS copolyesters. The block lengths of the resulting copolymers decreased with the severity of the treatment. Copolyesters with PET/PBS molar compositions of 90/10, 80/20, 70/30, and 50/50 were prepared by this method and their composition and microstructure were characterized by ¹H and ¹³C NMR, respectively. The T_g, T_m, and crystallinity of the copolymers decreased as the content in PBS and the degree of randomness increased. The elastic modulus and tensile strength of the copolymers decreased with the content of PBS, whereas, on the contrary, the elongation at break increased. The PET/PBS copolymers exhibited a pronounced hydrolytic degradability, which increased with the content in 1,4-butylene succinic units. Hydrolysis mainly occurred on the aliphatic ester groups.     

Synthesis,physico-chemical properties and biomedical applications of poly(amidoamine)s

The aim of this article is to provide a comprehensive survey on synthesis, chemical and physico-chemical properties, and applications in several fields, including the biomedical field, of a family of tertiary amino polymers, the poly(amido-amine)s.     

Aligned core/shell electrospinning of poly(glycerol sebacate)/poly(l‐lactic acid) with tuneable structural and mechanical properties

In an earlier study, scaffolds of biodegradable poly(glycerol sebacate) (PGS)/poly(l ‐lactic acid) (PLLA) core/shell fibres had been fabricated using a core/shell electrospinning method, and the scaffolds were found to have mechanical properties similar to those of natural soft tissues, excellent cytocompatibility and slow degradation rate. In this paper, PGS/PLLA core/shell fibre mats with tuneable degrees of fibre alignment were fabricated using core/shell electrospinning with a rotating fibre collection mandrel. An increase in the rotational speed raised the degree of fibre alignment in the fibre mats. Single and cyclic tensile testing of the mats showed that an increase in the fibre alignment raised the modulus, resilience, ultimate tensile strength (UTS) and elongation up to a maximum at 1000 or 1500 rpm, but the resilience, UTS and elongation decreased when the rotational speed was further raised to 2000 rpm. Nonlinearly elastic biomaterials with a large range of mechanical properties were successfully fabricated using this method and the aligned fibre structure may be capable of guiding the growth of attached cells. © 2016 Society of Chemical Industry     

Synthesis and properties of novel poly(tetramethylsilnaphthylenesiloxane) derivatives

Novel poly(tetramethylsilnaphthylenesiloxane) derivatives were synthesized and characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), and X-ray diffraction analyses. Poly(tetramethylsilnaphthylenesiloxane) derivatives were obtained by condensation polymerization of the corresponding disilanol derivatives, i.e. 1,4-, 1,5-, 2,6-, and 2,7-bis(dimethylhydroxysilyl)naphthalenes, which were prepared by the Grignard reaction using chlorodimethylsilane and the corresponding dibromonaphthalene derivatives followed by the hydrolyses, catalyzed by palladium on charcoal. The obtained poly(tetramethyl-1,5-silnaphthylenesiloxane) was insoluble in common organic solvents; however, the other polymers exhibited the good solubility in common organic solvents, such as tetrahydrofuran (THF), chloroform, dichloromethane, and toluene. The introduction of tetramethyl-1,5-silnaphthylenesiloxane units into the resulting polymer was confirmed by ¹H NMR spectrum of the copolymer obtained by condensation copolymerization of 1,5-bis(dimethylhydroxysilyl)naphthalene with 1,4-bis(dimethylhydroxysilyl)naphthalene. It was revealed from the DSC and X-ray diffraction measurements that poly(tetramethyl-1,5-silnaphthylenesiloxane) and poly(tetramethyl-2,6-silnaphthylenesiloxane) exhibited the crystallinity; however, poly(tetramethyl-1,4-silnaphthylenesiloxane) and poly(tetramethyl-2,7-silnaphthylenesiloxane) were amorphous. The glass transition temperature (T_g) and the temperature at 5% weight loss (T_d5) of poly(tetramethylsilnaphthylenesiloxane) derivatives with dimethylsilyl group at 1-position of the naphthylene moiety were higher than those at 2-position of the naphthylene moiety. The T_g and melting point (T_m) of the present polymers were higher than those of poly(tetramethyl-1,4-silphenylenesiloxane).     

Synthesis and properties of ABA-type triblock copolymers of poly(glycolide-co-caprolactone) (A) and poly(ethylene glycol) (B)

Poly(glycolide-co-caprolactone) (A)-poly(ethylene glycol) (B) ABA-type triblock copolymers (PGCE) were synthesized by bulk ring opening polymerization, using the hydroxyl endgroups of poly(ethylene glycol) (PEG) as initiator and stannous octoate as catalyst. The resulting copolymers were characterized by various analytical techniques. Gel permeation chromatographic analysis indicated that the polymerization product was free of residual monomers, PEG and oligomers. ¹H NMR and differential scanning calorimeter results demonstrated that the copolymers had a structure of poly(glycolide-co-caprolactone) (PGC) chains chemically attached to PEG segments. All the PGCE copolymers showed improved hydrophilicity in comparison with the corresponding PGC copolymers with the same molar ratio of glycolidyl and caproyl units. The microspheres of PGCE copolymer exhibited rough surfaces quite different from the smooth surface of PGC microspheres. This phenomenon was attentively ascribed to the highly swollen ability of PGCE copolymers and the freeze-drying process in the microspheres fabrication.     

聚癸二酸丙三醇酯的合成及电纺支架的制备

通过熔融共缩聚反应,将1∶1和1∶2两种摩尔比的丙三醇和癸二酸合成可生物降解的聚癸二酸丙三醇聚酯弹性体(PGS),并对其性能进行测定,1∶1组PGS与左旋聚乳酸(PLLA)共混,应用静电纺丝方法构建组织工程支架。结果表明,PGS弹性体具有优异的亲水性能和可生物降解性能,PLLA改性电纺的PGS支架符合组织工程支架材料的基本要求。     

Poly(N-vinylpyrrolidone)-grafted poly(N-isopropylacrylamide) copolymers: Synthesis, characterization and rapid deswelling and reswelling behavior of hydrogels

Poly(N-isopropylacrylamide)-block-poly(N-vinylpyrrolidone) diblock copolymer (PNIPAAm-b-PVPy) was successfully synthesized via sequential reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process, in which the chain transfer agent of xanthate was in situ afforded via the reaction of isopropylxanthic disulfide (DIP) with 2,2-azobisisobutylnitrile (AIBN). The RAFT/MADIX technique was employed to prepare the poly(N-vinylpyrrolidone)-grafted poly(N-isopropylacrylamide) copolymers (PNIPAAm-g-PVPy) with N,N-methylenebisacrylamide as the crosslinking agent. The comb-like PNIPAAm-g-PVPy copolymer networks with PVPy as the pendent chains were characterized by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS). The hydrogel behavior of PNIPAAm-g-PVPy networks was investigated in terms of swelling, deswelling and reswelling tests. With the inclusion of PVPy chains, the swelling ratios of the hydrogels were significantly enhanced compared to the control PNIPAAm hydrogel. It is found that the PVPy-modified PNIPAAm hydrogels displayed faster response to the external temperature changes than the control PNIPAAm hydrogel. The improved thermoresponsive properties of hydrogels are ascribed to the formation of the comb-like architectures in the copolymer networks.     

Alginate: properties and biomedical applications

Alginate is a biomaterial that has found numerous applications in biomedical science and engineering due to its favorable properties, including biocompatibility and ease of gelation. Alginate hydrogels have been particularly attractive in wound healing, drug delivery, and tissue engineering applications to date, as these gels retain structural similarity to the extracellular matrices in tissues and can be manipulated to play several critical roles. This review will provide a comprehensive overview of general properties of alginate and its hydrogels, their biomedical applications, and suggest new perspectives for future studies with these polymers.     

Syndiotactic poly(propene-co-norbornene): Synthesis and properties at low norbornene incorporation

Copolymerizations of propene with norbornene were carried out using a syndiotactic metallocene catalyst at low initial comonomer concentrations for different polymerization times. The influence of the norbornene concentration on the catalytic activity and on the resulting material properties has been analyzed. The copolymer molecular weight decreased drastically when small amounts of norbornene were added in reactions which lasted 30 min. When longer reaction times were used the molecular weight increased with time, however living polymerization was ruled out because the polydispersity was ca. 2. The DSC measurements showed copolymers with low crystallinity or which were completely amorphous.     

Synthesis,optical, electrochemical,and thermal stability properties of poly(azomethine-urethane)s

In this study, the novel low band gap and thermally stable poly(azomethine-urethane)s (PAMUs) were synthesized to investigate aliphatic and aromatic group effects on some physical properties such as thermal stability, optical and electrochemical properties. For this reason, we firstly synthesized the new Schiff bases via condensation reaction of 5-nitrovanilin with aromatic and aliphatic diamines. Then, these monomers were converted to PAMUs derivatives by the step-polymerization reaction with aromatic and aliphatic diisocyanates. The structures of the compounds were confirmed by FT-IR, UV–vis, ¹H NMR, and ¹³C NMR techniques. The molecular weight distribution parameters of the compounds were determined by the size exclusion chromatography (SEC). The compounds were also characterized by solubility tests, TG–DTA, and DSC techniques. Cyclic voltammetry (CV) measurements were carried out and HOMO–LUMO energy levels and electrochemical band gaps (E^′g${E^{\prime }}_g$) were calculated from their absorption edges. Additionally, optical band gaps (E_g) were determined by using UV–vis spectra of the materials. Fluorescence measurements were carried out in THF, DMF, and DMSO solutions to determine the optimum concentrations and the maximal emission and excitation intensities.     

Polyethers for biomedical applications: Bulk and surface characterisation of crosslinked blends of poly(ethylene oxide) and poly(propylene oxide)

Bulk and surface properties of crosslinked and non-crosslinked blends of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPOX) were studied for the elucidation of the behaviour of these materials in contact with blood. In the crosslinked blends the hydrophilic character increased with increasing PEO content, as concluded from swelling experiments and contact angle determinations. D.s.c. and dynamic mechanical measurements indicated the occurrence of phase separation in the blends and d.s.c. showed that on equilibration with water the PEO phase loses its crystallinity. F.t.-i.r.-a.t.r. analysis of the surface of crosslinked PPOX-PEO films showed an enrichment of the surface with PEO. These observations indicate that the good blood-compatibility of PPOX-PEO blends might be explained by the presence of an amorphous, PEO-enriched, hydrophilic surface.     

Synthesis and thermal properties of telechelic poly(lactic acid) ionomers

Telechelic poly(lactic acid) (PLA) ionomers were synthesized using a chemical recycling process. A transesterification reaction between a commercial PLA and 2-hydroxyethyl methacrylate or ethylene glycol was used to produce a hydroxy-terminated PLA. The hydroxy-terminated PLA was then reacted with itaconic anhydride to produce terminal carboxylic acid groups, which were neutralized with appropriate metal acetates to produce Na-, Li-, K-, Zn-, Ca- and Y-ω- and α,ω-telechelic PLA ionomers. ¹H NMR spectroscopy was used to confirm the presence of the itaconic acid end-groups and FTIR spectroscopy was used to quantify the extent of neutralization. The addition of the ionic groups increased the glass transition (T_g), and T_g increased as the strength of the ion-pair increased. The ionic groups suppressed crystallinity, especially when multivalent cations were used.     

Synthesis and optical properties of poly(tetramethylsilarylenesiloxane) derivative bearing diphenylcyclopentadithiophene moiety

The thermal and optical properties of a novel diphenylcyclopentadithiophene-based poly(tetramethylsilarylenesiloxane) derivative (P1), which was prepared via polycondensation of a novel disilanol monomer, i.e., 2,6-bis(dimethylhydroxysilyl)-4,4-diphenylcyclopentadithiophene (M1), were investigated. P1 exhibited good solubility in common organic solvents, such as benzene, toluene, chloroform, dichloromethane and THF at ambient temperature. The glass transition temperature (T_g) of P1 was determined by differential scanning calorimetry to be 109 °C. No melting temperature (T_m) of P1 was observed, indicating the obtained P1 was an amorphous polymer. The temperature at 5% weight loss (T_d5) of P1 was 454 °C, indicating the rather good thermostability of P1. Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra by introducing dimethylsilyl substituents onto 4,4-diphenylcyclopentadithiophene skeleton. The fluorescence quantum yields (Φ_Fs) of M1 and P1 in chloroform were determined to be 0.36 and 0.39, respectively. It was revealed that M1 and P1 exhibited the higher fluorescence intensity than diphenylcyclopentadithiophene owing to the cooperative effects of the introduction of diphenyl groups onto spiro carbon of cyclopentadithiophene as well as dimethylsilyl moieties onto 2- and 6-position of cyclopentadithiophene skeleton.     

Synthesis and properties of random poly(lactic acid)-based ionomers

A random poly(lactic acid), PLA, based ionomer was synthesized by copolymerizing a methacrylate-terminated PLA macromonomer and methyl methacrylate. The copolymerization kinetics were studied using ¹H NMR spectroscopy and the copolymer composition was characterized by ¹³C NMR spectroscopy. Carboxylic acid groups were introduced into the copolymer by reacting the hydroxyl end groups of the PLA macromonomer with succinic anhydride, and the acid groups were neutralized with metal acetates to produce Na-, Ca-, and Y-PLA ionomers. Significant increases in T_g were observed for the ionomers and thermomechanical analysis indicated that the ionomers were more resistant to penetration by a weighted probe and an apparent rubbery plateau was observed above T_g. The ionomers were more hydrophilic than PLA, but relatively low water absorption could be achieved for the Ca²⁺-salt ionomer.