AB‐ and ABC‐type di‐ and triblock copolymers of poly[styrene‐block‐(ε‐caprolactone)] and poly[styrene‐block‐(ε‐caprolactone)‐block‐lactide]: synthesis,characterization and thermal studies

Polystyrene terminated with benzyl alcohol units was employed as a macroinitiator for ring‐opening polymerization of ε‐caprolactone and L ‐lactide to yield AB‐ and ABC‐type block copolymers. Even though there are many reports on the diblock copolymers of poly(styrene‐block‐lactide) and poly(styrene‐block‐lactone), this is the first report on the poly(styrene‐block‐lactone‐block‐lactide) triblock copolymer consisting of two semicrystalline and degradable segments. The triblock copolymers exhibited twin melting behavior in differential scanning calorimetry (DSC) analysis with thermal transitions corresponding to each of the lactone and lactide blocks. The block derived from ε‐caprolactone also showed crystallization transitions upon cooling from the melt. In the DSC analysis, one of the triblock copolymers showed an exothermic transition well above the melting temperature upon cooling. Thermogravimetric analysis of these block copolymers showed a two‐step degradation curve for the diblock copolymer and a three‐step degradation for the triblock copolymer with each of the degradation steps associated with each segment of the block copolymers. The present study shows that it is possible to make pure triblock copolymers with two semicrystalline segments which also consist of degradable blocks. Copyright © 2009 Society of Chemical Industry     

Polyethylene‐block‐poly(ε‐caprolactone) diblock copolymers: synthesis and compatibility

A strategy is introduced for the synthesis of polyethylene‐block‐poly(ε‐caprolactone) block copolymers by a combination of coordination polymerization and ring‐opening polymerization. First, end‐hydroxylated polyethylene (PE‐OH) was prepared with a one‐step process through ethylene/3‐buten‐1‐ol copolymerization catalyzed by a vanadium(III) complex bearing a bidentate [N,O] ligand ([PhN?C(CH₃)CHC(Ph)O]VCl₂(THF)₂). The PE‐OH was then used as macroinitiator for ring‐opening polymerization of ε‐caprolactone, leading to the desired nonpolar/polar diblock copolymers. The block structure was confirmed by spectral analysis using ¹H NMR, gel permeation chromatography and differential scanning calorimetry. The unusual topologies of the model copolymers will establish a fundamental understanding for structure–property correlations, e.g. compatibilization, of polymer blends and surface and interface modification of other polymers. © 2014 Society of Chemical Industry     

Synthesis of star‐shaped poly(ε‐caprolactone)‐b‐poly(L‐lactide) copolymers: From star architectures to crystalline morphologies

Hexa‐armed star‐shaped poly(ε‐caprolactone)‐block‐poly(L ‐lactide) (6sPCL‐b‐PLLA) with dipentaerythritol core were synthesized by a two‐step ring‐opening polymerization. GPC and ¹H NMR data demonstrate that the polymerization courses are under control. The molecular weight of 6sPCLs and 6sPCL‐b‐PLLAs increases with increasing molar ratio of monomer to initiator, and the molecular weight distribution is in the range of 1.03–1.10. The investigation of the melting and crystallization demonstrated that the values of crystallization temperature (T_c), melting temperature (T_m), and the degree of crystallinity (X_c) of PLLA blocks are increased with the chain length increase of PLLA in the 6sPCL‐b‐PLLA copolymers. On the contrary, the crystallization of PCL blocks dominates when the chain length of PLLA is too short. According to the results of polarized optical micrographs, both the spherulitic growth rate (G) and the spherulitic morphology are affected by the macromolecular architecture and the length of the block chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of semi‐crystalline poly(ε‐caprolactone) and non‐crystalline polylactide blocks on the thermal properties of polydimethylsiloxane‐based block copolymers

Poly(A)‐block‐poly(B), poly(A)‐block‐poly(B)‐block‐poly(A) and B(A)₂ block copolymers were prepared through coordinated anionic ring‐opening polymerization of ε‐caprolactone (CL) and lactic acid (LA) using hydroxy‐terminated polydimethylsiloxane (PDMS) as initiator. A wide range of well‐defined combinations of PDMS‐block‐PCL and PDMS‐block‐PLA diblock copolymers, PCL‐block‐PDMS‐block‐PCL and PLA‐block‐PDMS‐block‐PLA triblock copolymers and star‐PDMS(PCL)₂ copolymers were thus obtained. The number‐average molar masses and the structure of the synthesized block copolymers were identified using various analytical techniques. The thermal properties of these copolymers were established using differential scanning calorimetry. Considering PDMS‐block‐PCL copolymers, the results demonstrate the complex effect of polymer architecture and PCL block length on the ability of the PDMS block to crystallize or not. In the case of diblock copolymers, crystallization of PCL blocks originated from stacking of adjacent chains inducing the extension of the PDMS block that can easily crystallize. In the case of star copolymers, the same tendency as in triblock copolymers is observed, showing a limited crystallization of PDMS when the length of the PCL block increases. In the case of PDMS‐block‐PLA copolymers, melting and crystallization transitions of the PLA block are never observed. Considering the diblock copolymers, PDMS sequences have the ability to crystallize. © 2019 Society of Chemical Industry     

Synthesis and characterization of new biodegradable comb‐dendritic triblock copolymers

A series of well‐defined dumbbell‐shaped triblock copolymers consisting of linear poly(ethylene glycol) (PEG) and comb‐like poly(ε‐caprolactone) (PCL) with varied PCL arm lengths have been synthesized via the sequential preparation of different generation terminal dendronized PEG and ring‐opening polymerization of ε‐caprolactone. The copolymers were characterized using Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopy and gel permeation chromatography. Differential scanning calorimetry was performed to measure the glass transition temperature, melting point and degree of crystallinity and the PEG segment and PCL segment crystallization temperatures. The crystallization of the copolymers was also studied using X‐ray diffraction. The dumbbell‐shaped copolymers were further used to construct microspheres using a double emulsion method. Scanning electron microscopy and dynamic light scattering results showed the size of the microspheres was about 2 to 4 µm and the size distribution was quite narrow. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of novel lipid functionalized poly(ε‐caprolactone)s

A series of novel lipid functionalized poly(ε‐caprolactone)s (PCLs) were synthesized through ROP of ε‐caprolactone in the presence of threo‐9,10‐dihydroxyoctadecanoic acid, synthesized from oleic acid. PCLs with different molecular weights were obtained by controlling the molar ratio of the initiator to the monomer. DSC and XRD analysis indicate that the crystallinity of PCLs decreased when compared to unfunctionalized PCL. The enzymatic degradation study shows that for samples with lower lipid derivatives content, a higher enzymatic degradation rate was observed because the lipase enzymes attack the ester bonds of the polymer; increased lipid content therefore inhibits the action of the lipase enzymes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

α‐Amino acids as initiators of ε‐caprolactone and L,L‐lactide polymerization

Biodegradable polymers/oligomers were successfully synthesized through a ring‐opening polymerization of ε‐caprolactone and L ,L ‐lactide, initiated by L ‐arginine and L ‐citrulline. The α‐amino acid initiators are natural, operationally simple, inexpensive, environmentally friendly and safe for human health. The polymerizations were performed with no solvents and without introducing any metal impurities. The chemical structures of the polymers obtained were elucidated using ¹H NMR, ¹³C NMR and Fourier transform infrared spectroscopies. In addition, incorporation of α‐amino acid molecules into the polymer chain was confirmed using matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry. Due to the significant biological activity of L ‐arginine and L ‐citrulline, these α‐amino acid initiators may open a new route for the synthesis of functional polymers especially for pharmaceutical applications. Copyright © 2011 Society of Chemical Industry     

Synthesis and characterization of poly[(R,S)‐3‐hydroxybutyrate] telechelics and their use in the synthesis of poly(methyl methacrylate)‐b‐ poly(3‐hydroxybutyrate) block copolymers

Poly[(R,S)‐3‐hydroxybutyrate] oligomers containing dihyroxyl (PHB‐diol), dicarboxylic acid (PHB‐diacid) and hydroxyl‐carboxylic acid (a‐PHB) end functionalities were obtained by the anionic polymerization of β‐butyrolacton (β‐BL). Ring opening anionic polymerization of β‐BL was initiated by a complex of 18‐Crown‐6 with γ‐hydroxybutyric acid sodium salts (for PHB‐diol and a‐PHB) or succinic acid disodium salt (for PHB‐diacid). Dihydroxyl functionalization was formed by the termination of polymerization with bromo‐ethanol or bromo‐decanol while the others were done by protonation. Hydroxyl and/or carboxylic acid functionalized PHB oligomers with ceric salts were used to initiate the polymerization of methylmethacrylate (MMA). PHB‐b‐PMMA block copolymers obtained by this way were purified by fractional precipitation and characterized using ¹H‐NMR and ¹³C‐NMR, gel permeation chromatography (GPC), and thermal analysis (DSC and TGA) techniques. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 965–973, 2002     

Soft nanoconfinement effects on the crystallization behavior of asymmetric poly(ethylene oxide)‐block‐poly(ε‐ caprolactone) diblock copolymers

The time‐ and temperature‐related crystallization process for the structure transitions of asymmetric crystalline‐crystalline diblock copolymers from the melt to crystallites was investigated with synchrotron simultaneous small‐angle/wide‐angle X‐ray scattering. Two asymmetric poly(ethylene oxide)‐poly(ε‐caprolactone) diblock copolymers were chosen. It is found in the course of the copolymer crystallization that the shorter blocks are uncrystallizable in both of the asymmetric diblock copolymers and final lamellar structures are formed in both of them. The final lamellar structure was confirmed from atomic force microscopy observations. The small‐angle X‐ray scattering data collected were analyzed with different methods for the early stage of crystallization. Guinier and Debye‐Bueche plots indicate that there are neither isolated domains nor correlated domains formed before the formation of lamellae in the asymmetric diblock copolymers during the crystallization process. The structure evolution was calculated according to the correlation function, and the soft nanoconfined crystallization behavior is discussed. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of ABA type tri‐block copolymers derived from p‐dioxanone,L‐lactide and poly(ethylene glycol)

A series of triblock co‐polymers, consisting of a poly(ethylene glycol) (PEG) central block joined to two blocks of random p‐dioxanone‐co‐L ‐lactide copolymers were synthesized by ring‐opening polymerization of p‐dioxanone (PDO) and L ‐lactide (LLA) initiated by PEG in the presence of stannous 2‐ethylhexanoate catalyst. The resulting copolymers were characterized by various techniques including ¹H and ¹³C NMR and FTIR spectroscopies, gel permeation chromatography, inherent viscosity, wide‐angle X‐ray diffractometry (WAXD) and differential scanning calorimetry (DSC). The conversion of PDO and L ‐lactide into the polymer was studied various mole ratios and at different polymerization temperature from ¹H NMR spectra. Results of WAXD and DSC showed that the crystallinity of PEG macroinitiator was greatly influenced by the composition of PDO and L ‐lactide in the copolymer. The triblock copolymers with low molecular weight were soluble in water at below room temperature. © 2003 Society of Chemical Industry     

Synthesis,crystallinity and degradation properties of biodegradable poly[(sebacic anhydride)‐co‐caprolactone] triblock copolymers

BACKGROUND: A series of novel biodegradable poly[(sebacic anhydride)‐co‐caprolactone] (PSA‐co‐PCL) triblock copolymers were prepared by melt condensation of acylated PSA and monofunctional hydroxyl‐terminated PCL prepolymers. These copolymers could be used as novel drug delivery carriers with expected good drug permeability due to the PCL component. The degradation rate and mode can be modulated by varying the ratio of monomers in the copolymer. RESULTS: The homopolymers and copolymers were characterized using ¹H NMR, gel permeation chromatography and differential scanning calorimetry (DSC). ¹H NMR confirmed the formation of triblock copolymers that comprise a middle PSA block and two side PCL blocks. DSC revealed that the melting temperature and degree of crystallinity for both sebacic anhydride (SA) and caprolactone (CL) components are strongly composition dependent, implying the hindrance effect of the two components on the crystallinity. In vitro degradation experiments showed that the mass loss is significantly accelerated for samples in base buffer solution and more rapid for the copolymers with a higher SA content. Scanning electron microscopy revealed that for SA‐rich copolymer, PSA(80 wt%)‐co‐PCL, surface erosion dominated the degradation mode of the sample. In contrast, for CL‐rich copolymer, PSA(20 wt%)‐co‐PCL, a micropore structure developed at a degradation time of 155 h along the edges of the sample, owing to the hydrolysis of SA. CONCLUSION: It is concluded that the rate and mode of degradation of these copolymers can be tuned by varying the composition of the copolymers. Copyright © 2007 Society of Chemical Industry     

Crystalline properties of poly(ε‐caprolactone)‐block‐poly(vinyl acetate) block copolymers: influence of synthesis route

Poly(ε‐caprolactone)‐block‐poly(vinyl acetate) (PCL‐b‐PVAc) block copolymers were synthesized using two approaches: a ‘coupling’ approach using click chemistry reaction and a ‘macroinitiator’ route. Different copolymers, varying by their block lengths, were prepared with both methods. PCL is a semi‐crystalline polymer, and consequently PCL blocks of PCL‐b‐PVAc are able to crystallize. The purpose of this work was to analyse the influence of the method of copolymer synthesis on the crystallinity of the PCL blocks. The results indicate a significant decrease of the crystallinity of the PCL blocks in copolymers obtained using the coupling method, compared to PCL homopolymers, in contrast to copolymers obtained through the macroinitiator approach for which the crystallinity of PCL is much less affected. This influence of the synthesis method is explained by the presence, in the copolymers obtained using the click reaction, of a rigid triazol cycle binding the two blocks, limiting their mobility and decreasing the tendency of PCL to crystallize. © 2013 Society of Chemical Industry     

Effects of plasma treatment on biocompatibility of poly[(L‐lactide)‐co‐(ϵ‐caprolactone)] and poly[(L‐lactide)‐co‐glycolide] electrospun nanofibrous membranes

Poly[(l ‐lactide)‐co ‐(? ‐caprolactone)] (PLCL) and poly[(l ‐lactide)‐co ‐glycolide] (PLGA) copolymers are widely used in neural guide tissue regeneration. In this research, the surface modification of their hydrophilicity was achieved using plasma treatment. Attachment and proliferation of olfactory ensheathing cells on treated electrospun membranes increased by 26 and 32%, respectively, compared to the untreated PLCL and PLGA counterparts. Cells cultivated on both the PLCL and PLGA membranes showed high viability (>95%) and healthy morphologies with no evidence of cytotoxic effects. Cells grown on treated electrospun fibres displayed significant increases in mitochondrial activity and reductions in membrane leakage when compared to untreated samples. The results suggested that plasma treatment of the surface of the polymers enhanced both cell viability and growth without incurring any cytotoxic effects. © 2017 Society of Chemical Industry     

Synthesis and characterization of amine‐functionalized amphiphilic block copolymers based on poly(ethylene glycol) and poly(caprolactone)

A series of amine‐functionalized block copolymers, poly(caprolactone)‐block‐poly(ethylene glycol) (PCL‐b‐PEG), were synthesized by ring‐opening bulk polymerization (ROP) of ε‐caprolactone (ε‐CL) initiated through the hydroxyl end of the amino poly(ethylene glycol) (PEG) used as a macroinitiator in the presence of stannous 2‐ethylhexonoate [Sn(Oct)₂]. The polymerization and end functionality of the polymer were studied by different physicochemical techniques (¹H NMR, Fourier transform infrared and X‐ray photoelectron spectroscopy, gel permeation chromatography and thermogravimetric analysis). Thermal, crystalline and mechanical properties of the polymer were thoroughly analyzed using differential scanning calorimetry, wide‐angle X‐ray diffractometry and tensile testing, respectively. The results showed a linear improvement in crystallinity and mechanical properties of the polymer with the content of PEG. Thus the synthesized functional polymers can be used as excellent biomaterials for the delivery of polyanions, as well as macroinitiators for the synthesis of A–B–C‐type block copolymers. Copyright © 2006 Society of Chemical Industry     

Structure and morphology of poly(β‐hydroxybutyrate) synthesized by ring‐opening polymerization of racemic (R,S)‐β‐butyrolactone with distannoxane derivatives

Predominantly syndiotactic poly((R,S)‐β‐hydroxybutyrate) (PHB) was synthesized by ring‐opening polymerization of racemic β‐butyrolactone with distannoxane derivatives as catalysts. We have studied the polymerization of (R,S)‐β‐BL using distannoxane derivatives as catalysts and the effects of polymerization time on crude yield and molecular weight of the polymers obtained. Then, a more detailed study of the characterization of polymers obtained using hydroxy‐ and ethoxy‐distannoxanes was performed. ¹³C NMR spectroscopy resolved stereosequences in synthetic PHB at the diad level for the carbonyl carbon and at the triad level for the methylene carbon. These analyses show that distannoxane catalysts produce preferentially syndiotactic polyesters (syndiotactic diads fraction from 0.56 to 0.61). Triad stereosequence distribution of PHB samples agrees favourably with the Bernoullian statistical model of chain‐end control, where ideally Φ = 4(mm) (rr)/(mr + rm)² = 1 for perfect chain‐end control. Polymer samples synthesized from distannoxane catalysts are composed of two distinct transition endotherm components with peak temperatures of approximately 42 °C and 75 °C. The formation of two melting endotherms may be due to the presence of two different crystalline structures. © 2000 Society of Chemical Industry     

A novel initiating system for ring‐opening polymerization of ε‐caprolactone: Synthesis of triarm star‐shaped poly(ε‐caprolactone)

The rare earth compound, scandium trifluoromethanesulfonate [Sc(OTf)₃], has been used as a water‐tolerant catalyst for the synthesis of star‐shaped poly(ε‐caprolactone)s (SPCLs) with trimethylol propane as trifunctional initiator in solvent at 40°C. Triarm SPCLs have been successfully prepared. The molar mass of SPCLs were determined by end‐group ¹H NMR analyses, which could be well controlled by the molar ratio of the monomer to the initiator, and were independent of the amount of Sc(OTf)₃ used. Differential scanning calorimetry analyses suggested that the maximal melting point, the cold crystallization temperature, and the degree of crystallinities of SPCLs increased with the increasing of the molar mass and were lower than the linear poly(ε‐caprolactone) (LPCL) with similar molar mass. Furthermore, polarized optical microscopy indicated that LPCL showed fast crystallization rate and good spherulitic morphology with apparent Maltese cross pattern, whereas SPCLs exhibit much lower crystallization rate and poor spherulitic morphology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of α‐amino acid‐containing polyester: poly[(ε‐caprolactone)‐co‐(serine lactone)]

Novel polyesters, poly[(ε‐caprolactone)‐co‐(N‐trityl‐L ‐serine‐β‐lactone)]s, were prepared by copolymerizing ε‐caprolactone (CL) with N‐trityl‐L ‐serine‐β‐lactone (TSL) using ZnEt₂ as the catalyst. The number‐average molecular weights were determined which ranged from 2.7 × 10⁴ to 4.9 × 10⁴ Da with dispersity values ranging from 1.6 to 1.8. The structures of the copolymers were investigated by means of ¹H NMR, ¹³C NMR and infrared spectroscopies, thermogravimetric analysis and differential scanning calorimetry. The results indicated that CL and TSL monomer units were randomly distributed within the copolymer backbone structures and the ratios of TSL to CL in the copolymers were close to those in the feeds. After removal of the trityl group under mild condition, a new polyester with side amino groups provided by serine units was obtained. L929 cell culturing test indicated good biocompatibility of the polyester with or without protective groups. © 2012 Society of Chemical Industry     

Synthesis and characterization of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers with dibutylmagnesium as catalyst

Two series of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers were prepared by the ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) and dibutylmagnesium in 1,4‐dioxane solution at 70°C. The triblock structure and molecular weight of the copolymers were analyzed and confirmed by ¹H NMR, ¹³C NMR, FTIR, and gel permeation chromatography. The crystallization and thermal properties of the copolymers were investigated by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). The results illustrated that the crystallization and melting behaviors of the copolymers were depended on the copolymer composition and the relative length of each block in copolymers. Crystallization exothermal peaks (T_c) and melting endothermic peaks (T_m) of PEG block were significantly influenced by the relative length of PCL blocks, due to the hindrance of the lateral PCL blocks. With increasing of the length of PCL blocks, the diffraction and the melting peak of PEG block disappeared gradually in the WAXD patterns and DSC curves, respectively. In contrast, the crystallization of PCL blocks was not suppressed by the middle PEG block. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Visible light‐absorbing biocompatible polymers based on L‐lactide and aminosugars: preparation and characterization

Two series of polymers with low‐molecular‐weight L ‐lactide side‐arms were prepared by ring‐opening polymerization using D ‐glucosamine and N‐acetyl‐D ‐glucosamine as polymer core molecules, and methanesulfonic acid as solvent and catalyst. This simple synthetic route does not rely on the use of organometallic catalysts, and has also proven useful to the authors for chitosan grafting with lactones. NMR spectroscopy reveals a high degree of substitution (>3), and Fourier transform infrared/NMR spectra suggest the existence of three different lactate tautomers likely to be responsible for coloration. These D ‐glucosamine‐based polymers also display glass transition temperatures approximately 10 °C above that of the human body, which points to the potential of these lactone‐grafted aminosugars with tunable amphiphilic character in the design of submicrometer‐sized drug delivery vehicles. They are also viewed as interesting hydrophobic chelating agents for catalytic transition metal centers. Copyright © 2010 Society of Chemical Industry     

Effects of copolymer microstructure on the properties of electrospun poly(l‐lactide‐co‐ε‐caprolactone) absorbable nerve guide tubes

The main objective of this work has been to study the effects of copolymer microstructure, both chemical and physical, on the microporosity, in vitro hydrolytic degradability and biocompatibility of electrospun poly(l ‐lactide‐co‐ε‐caprolactone), PLC, copolymer tubes for potential use as absorbable nerve guides. PLC copolymers with L : C compositions of 50 : 50 and 67 : 33 mol % were synthesized via the ring‐opening copolymerization of l ‐lactide (L) and ε‐caprolactone (C) at 120°C for 72 h using stannous octoate (tin(II) 2‐ethylhexanoate) and n‐hexanol as the initiating system. Electrospinning was carried out from solution in a dichloromethane/dimethylformamide (7 : 3 v/v) mixed solvent at room temperature. The in vitro hydrolytic degradation of the electrospun PLC tubes was studied in phosphate buffer saline over a period of 36 weeks. The microporous tubes were found to be gradually degradable by a simple hydrolysis mechanism leading to random chain scission. At the end of the degradation period, the % weight retentions of the PLC 50 : 50 and 67 : 33 tubes were 15.6% and 70.2%, respectively. Pore stability during storage as well as cell attachment and proliferation of mouse fibroblast cells (L929) showed the greater potential of the PLC 67 : 33 tubes for use as temporary scaffolds in reconstructive nerve surgery. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4357–4366, 2013