Multicarboxylic aromatic acid core initiator for the synthesis of star‐shaped poly(ϵ‐caprolactone) with carboxyl end groups

We successfully carried out the ring‐opening polymerization of ?‐caprolactone with 1,3,5‐benzenetricarboxylic acid and 1,2,4,5‐benzenetetracarboxylic acid as the core initiators at 225°C in bulk, and three‐armed and four‐armed star poly(?‐caprolactone)s [poly(?‐CL)s] with carboxyl end groups were obtained. No transesterification, which would have led to a decrease in the molecular weight of poly(?‐CL), was found. The effects of the polymerization conditions on the polymerization are discussed; the poly(?‐CL)s were characterized by ¹H‐NMR, gel permeation chromatography, and thermogravimetric analysis in detail. A mechanism of alkyl–oxygen bond scission by the nucleophilic attack of the carboxyl anions via hydrogen proton transfer is presented for this system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3713–3717, 2006     

Synthesis,characterization and crosslinking of functional star‐shaped poly(ε‐caprolactone)

Star‐shaped low molecular weight poly(ε‐caprolactone)s (PCLs) were synthesized and functionalized with crosslinkable terminal groups for subsequent crosslinking. The ε‐caprolactone (CL) prepolymers were polymerized by ring‐opening in the presence of polyglycerine (PGL) as an initiator (1, 3 and 5 mol%) and Sn(II)2‐ethylhexanoate as a catalyst. Characterization of the prepolymer by ¹³C/¹H nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) revealed a six‐armed star‐shaped structure for the prepolymer with the molecular weight controlled by the ratio of PGL and CL. Functionalization of the hydroxyl‐terminated prepolymer was carried out with maleic or itaconic anhydride. In both cases, the characterization of the functionalized prepolymer showed that the hydroxyl groups were completely substituted. The functionalized PCLs were successfully crosslinked through the reaction of double bonds. The crosslinking was induced either thermally with organic peroxide or photochemically with a photosensitive initiator. Characterization of the crosslinked PCLs by Soxhlet extraction, DSC and FTIR showed that the itaconic double bond was much more reactive in thermal crosslinking than the maleic double bond. Thus, the crosslinked prepolymers that were functionalized with itaconic double bonds achieved a gel content of about 90%. A gel content of 100% was achieved with several compositions where crosslinking agents were employed. © 2002 Society of Chemical Industry     

Poly(ϵ‐caprolactone)‐functionalized carbon nanofibers by surface‐initiated ring‐opening polymerization

Carbon nanofibers (CNFs) were covalently functionalized with biodegradable poly(?‐caprolactone) (PCL) by in situ ring‐opening polymerization (ROP) of ?‐caprolactone in the presence of stannous octoate. Surface oxidation treatment of the pristine CNFs afforded carboxylic CNFs (CNF‐COOH). Reaction of CNF‐COOH with excess thionyl chloride (SOCl₂) and glycol produced hydroxyl‐functionalized CNFs (CNF‐OH). Using CNF‐OH as macroinitiator, PCL was covalently grafted from the surfaces of CNFs by ROP, in either the presence or absence of sacrificial initiator, butanol. The grafted PCL content was achieved as high as 64.2 wt %, and can be controlled to some extent by adjusting the feed ratio of monomer to CNF‐OH. The resulting products were characterized by FTIR, NMR, Raman spectroscopy, TGA, DSC, SEM, TEM, HRTEM, and XRD. Core–shell nanostructures were observed under HRTEM for the PCL‐functionalized CNFs because of the thorough grafting. The PCL‐grafted CNFs showed different melting and crystallization behaviors from the mechanical mixture of PCL and CNF‐OH. This approach to PCL‐functionalized CNFs opens an avenue for the synthesis, modification, and application of CNF‐based nanomaterials and biomaterials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of ABA triblock and novel multiblock copolymers from ethylene glycol,L‐lactide,and ϵ‐caprolactone

Three types of copolymers were synthesized and characterized. First, triblock ABA copolymers [where A is a homopolymer of ?‐caprolactone and B is poly(ethylene glycol)] were prepared by the ring‐opening polymerization of poly(ethylene glycol) with ?‐caprolactone in the presence of stannous octoate (Sn(Oct)₂). The spectral, thermal, and mechanical properties of one sample of these copolymers were studied, and it was discovered that these types of copolymers were more hydrophilic, possessed lower melting points, and had superior mechanical properties (greater toughness) than poly(?‐caprolactone). Second, triblock ABA copolymers [where A is a homopolymer of L ‐lactide and B is poly(ethylene glycol)] were prepared by the ring‐opening polymerization of poly(ethylene glycol) with L ‐lactide in the presence of Sn(Oct)₂. The mechanical properties of these copolymers were studied, and it was found that they were tougher and softer than poly(L ‐lactide). Third, novel ABA triblock copolymers [where A is a copolymer of ?‐caprolactone and L ‐lactide and B is poly(ethylene glycol)] were prepared, and ¹H‐NMR and ¹³C‐NMR spectra of these copolymers indicated a microblock structure for the two end blocks. The stress–strain behavior revealed low yields and high toughness for these copolymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2072–2081, 2002     

Preparation of new dendrimer‐like star‐shaped amphiphilic poly(ethylene glycol)–poly(ϵ‐caprolactone) copolymers for biocompatible and high‐efficiency curcumin delivery

Novel amphiphilic star‐shaped terpolymers comprised of hydrophobic poly(?‐caprolactone), pH‐sensitive polyaminoester block and hydrophilic poly(ethylene glycol) (M_n = 1100, 2000 g mol^?1) were synthesized using symmetric pentaerythritol as the core initiator for ring‐opening polymerization (ROP) reaction of ?‐caprolactone functionalized with amino ester dendrimer structure at all chain ends. Subsequently, a second ROP reaction was performed by means of four‐arm star‐shaped poly(?‐caprolactone) macromer with eight ‐OH end groups as the macro‐initiator followed by the attachment of a poly(ethylene glycol) block at the end of each chain via a macromolecular coupling reaction. The molecular structures were verified using Fourier transform infrared and ¹H NMR spectroscopies and gel permeation chromatography. The terpolymers easily formed core–shell structural nanoparticles as micelles in aqueous solution which enhanced drug solubility. The hydrodynamic diameter of these agglomerates was found to be 91–104 nm, as measured using dynamic light scattering. The hydrophobic anticancer drug curcumin was loaded effectively into the polymeric micelles. The drug‐loaded nanoparticles were characterized for drug loading content, encapsulation efficiency, drug–polymer interaction and in vitro drug release profiles. Drug release studies showed an initial burst followed by a sustained release of the entrapped drug over a period of 7days at pH = 7.4 and 5.5. The release behaviours from the obtained drug‐loaded nanoparticles indicated that the rate of drug release could be effectively controlled by pH value. Altogether, these results demonstrate that the designed nanoparticles have great potential as hydrophobic drug delivery carriers for cancer therapy. © 2015 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     

Synthesis of poly(ester‐anhydride)s based on poly(ϵ‐caprolactone) prepolymer

The objective of this study was to prepare high molecular weight poly(ester‐anhydride)s by melt polycondensation. The polymerization procedure consisted of the preparation of carboxylic acid terminated poly(?‐caprolactone) prepolymers that were melt polymerized to poly(?‐caprolactone)s containing anhydride functions along the polymer backbone. Poly(?‐caprolactone) prepolymers were prepared using either 1,4‐butanediol or 4‐(hydroxymethyl)benzoic acid as initiators, yielding hydroxyl‐terminated intermediates that were then converted to carboxylic acid‐terminated prepolymers by reaction with succinic anhydride. Prepolymers were then allowed to react with an excess of acetic anhydride, followed by subsequent polycondensation to resulting high molecular weight poly(ester‐anhydride)s. Upon coupling of prepolymers, size exclusion chromatography analyses showed an increase from 3600 to 70,000 g/mol in number‐average molecular weight (M_n) for the 1,4‐butanediol initiated polymer, and an increase from 7200 to 68,000 g/mol for the 4‐(hydroxymethyl)benzoic acid‐initiated polymer. 4‐Hydroxybenzoic acid and adipic acid were also used as initiators in the preparation of poly(?‐caprolactone) prepolymers. However, with these initiators, the results were not satisfactory. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 176–185, 2001     

Poly(ethylene terephthalate)–poly(caprolactone) block copolymer. I. Synthesis,reactive extrusion,and fiber morphology

A novel poly(ethylene terephthalate)–poly(caprolactone) block copolymer (PET–PCL) is synthesized in a reactive twin‐screw extrusion process. In the presence of stannous octoate, ring‐opening polymerization of ϵ‐caprolactone is initiated by the hydroxyl end groups of molten PET to form polycaprolactone blocks. A block copolymer with minimal transesterification is obtained in a twin‐screw extruder as a consequence of the fast distributive mixing of ϵ‐caprolactone into high melt viscosity PET and the short reaction time. The PET–PCL structure is characterized by IV, GPC, ¹H‐NMR, and DSC. Fully drawn and partially relaxed fibers spun from PET–PCL are characterized by WAXD and SAXS. A substantial decrease in the oriented amorphous fraction appears to be the major structural change in the relaxed fiber that provides the fiber with the desired stress–strain characteristics. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1858–1867, 1999     

Synthesis and characterization of poly(ϵ‐caprolactone)–poly(L‐lactide) diblock copolymers with an organic amino calcium catalyst

The quasiliving characteristics of the ring‐opening polymerization of ?‐caprolactone (CL) catalyzed by an organic amino calcium were demonstrated. Taking advantage of this feature, we synthesized a series of poly(?‐caprolactone) (PCL)–poly(L ‐lactide) (PLA) diblock copolymers with the sequential addition of the monomers CL and L ‐lactide. The block structure was confirmed by ¹H‐NMR, ¹³C‐NMR, and gel permeation chromatography analysis. The crystalline structure of the copolymers was investigated by differential scanning calorimetry and wide‐angle X‐ray diffraction analysis. When the molecular weight of the PLA block was high enough, phase separation took place in the block copolymer to form PCL and PLA domains, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2654–2660, 2006     

Synthesis of graft and block copolymers from 2‐dimethylaminoethyl methacrylate and caprolactone

This paper outlines the synthesis of a range of graft and block copolymers containing 2‐dimethylaminoethyl methacrylate and caprolactone sequences by means of two distinct strategies. In the first place, common to both pathways, low‐molar‐mass hydroxyl end‐capped polycaprolactone (PCL‐OH) was prepared by the ring‐opening polymerization of caprolactone in the presence of an aluminium alkoxide Schiff's base (HAPENAlOⁱPr) as initiator followed by hydrolysis of the Al? O bond. For the synthesis of copolymers with a main vinyl carbon–carbon backbone and PCL grafts, PCL‐OH was initially converted into ω‐methacryl‐PCL using methacryloyl chloride. This macromonomer was then copolymerized with 2‐dimethylaminoethyl methacrylate (DMAEMA) by atom transfer radical polymerization (ATRP). For the synthesis of block copolymers, PCL‐OH was first transformed into a bromine end‐capped PCL (PCL‐Br) with 2‐bromoisobutyryl bromide. PCL‐Br was then used as macroinitiator in various concentrations for the ATRP of 2‐dimethylaminoethyl methacrylate, thus leading to PCL and poly(DMAEMA) blocks of varying lengths. The formation of both graft and block copolymers was thoroughly checked using NMR and size exclusion chromatography. Copyright © 2007 Society of Chemical Industry     

Self‐assembled micelles prepared from poly(ɛ‐caprolactone)–poly(ethylene glycol) and poly(ɛ‐caprolactone/glycolide)–poly(ethylene glycol) block copolymers for sustained drug delivery

A series of poly(?‐caprolactone)–poly(ethylene glycol) (PCL‐PEG) and poly(?‐caprolactone/glycolide)–poly(ethylene glycol) [P(CL/GA)‐PEG] diblock copolymers were prepared by ring‐opening polymerization of ?‐caprolactone or a mixture of ?‐caprolactone and glycolide using monomethoxy PEG (mPEG) as macroinitiator and Sn(Oct)₂ as catalyst. The resulting copolymers were characterized using ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and wide‐angle X‐ray diffraction. Copolymer micelles were prepared using the nanoprecipitation method. The morphology of the micelles was spherical or worm‐like as revealed by transmission electron microscopy, depending on the copolymer composition and the length of the hydrophobic block. Introduction of the glycolide component, even in small amounts (CL/GA = 10), disrupted the chain structure and led to the formation of spherical micelles. Interestingly, the micelle size decreased with the encapsulation of paclitaxel. Micelles prepared from mPEG5000‐derived copolymers exhibited better drug loading properties and slower drug release than those from mPEG2000‐derived copolymers. Drug release was faster for copolymers with shorter PCL blocks than for those with longer PCL chains. The introduction of glycolide moieties enhanced drug release, but the overall release rate did not exceed 10% in 30 days. In contrast, drug release was enhanced in acidic media. Therefore, these bioresorbable micelles and especially P(CL/GA)‐PEG micelles with excellent stability, high drug loading content, and prolonged drug release could be promising for applications as drug carriers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45732.     

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     

Non‐covalent interactions of pyrene end‐labeled star poly(ɛ‐caprolactone)s with fullerene

Pyrene end‐labeled star poly(?‐caprolactone)s (PCLs) with polyhedral oligomeric silsesquioxane (POSS) core were prepared by combination of copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) click chemistry and ring‐opening polymerization techniques. First, ?‐caprolactone (?‐CL) is polymerized by using 1‐pyrene methanol as initiator and stannous octoate as catalyst to obtain α‐pyrene‐ω‐hydroxyl telechelic PCL with different chain lengths. Then, its hydroxyl group is converted to acetylene functionality by esterification reaction with propargyl chloroformate. Finally, the CuAAC click reaction of α‐pyrene‐ω‐acetylene telechelic PCL with POSS‐(N₃)₈ leads to corresponding pyrene end‐labeled star‐shaped PCLs. The successful synthesis of pyrene end‐labeled star polymers is clearly confirmed by ¹H‐nuclear magnetic resonance, Fourier transform infrared, gel permeation chromatograph, differential scanning calorimeter, and thermogravimetric analysis. Furthermore, non‐covalent interactions of obtained star polymers with fullerene are investigated in liquid media. Based on Raman spectroscopy and visual investigations, the star polymer having shorter chain length exhibited better and more stable dispersion with fullerene. The amount of pyrene units present per polymer chains can directly influence the dispersion stability of fullerene. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46520.     

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     

Biodegradable polyester layered silicate nanocomposites based on poly(ϵ‐caprolactone)

Nanocomposites based on biodegradable poly(?‐caprolactone) (PCL) and layered silicates (montmorillonite, MMT) were prepared either by melt interaction with PCL or by in situ ring‐opening polymerization of ?‐caprolactone as promoted by the so‐called coordination‐insertion mechanism. Both non‐modified clays (Na⁺ ‐MMT) and silicates modified by various alkylammonium cations were studied. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. Even at a filler content as low as 3 wt% of inorganic layered silicate, the PCL‐layered silicate nanocomposites exhibited improved mechanical properties (higher Young's modulus) and increased thermal stability as well as enhanced flame retardant characteristics as a result of a charring effect. It was shown that the formation of PCL‐based nanocomposites depended not only on the nature of the ammonium cation and related functionality but also on the selected synthetic route, melt intercalation vs. in situ intercalative polymerization. Interestingly enough, when the intercalative polymerization of ?‐caprolactone was carried out in the presence of MMT organo‐modified with ammonium cations bearing hydroxyl functions, nanocomposites with much improved mechanical properties were recovered. Those hybrid polyester layered silicate nanocomposites were characterized by a covalent bonding between the polyester chains and the clay organo‐surface as a result of the polymerization mechanism, which was actually initiated from the surface hydroxyl functions adequately activated by selected tin (II) or tin (IV) catalysts.     

Synthesis and characterization of temperature‐sensitive block copolymers from poly(N‐isopropylacrylamide) and 4‐methyl‐ε‐caprolactone or 4‐phenyl‐ε‐caprolactone

This study synthesizes thermally sensitive block copolymers poly(N‐isopropylacrylamide)‐b‐poly(4‐methyl‐ε‐caprolactone) (PNIPA‐b‐PMCL) and poly(N‐isopropylacrylamide)‐b‐poly(4‐phenyl‐ε‐caprolactone) (PNIPA‐b‐PBCL) by ring‐opening polymerization of 4‐methyl‐ε‐caprolactone (MCL) or 4‐phenyl‐ε‐caprolactone (BCL) initiated from hydroxy‐terminated poly(N‐isopropylacrylamide) (PNIPA) as the macroinitiator in the presence of SnOct₂ as the catalyst. This research prepares a PNIPA bearing a single terminal hydroxyl group by telomerization using 2‐hydroxyethanethiol (ME) as a chain‐transfer agent. These copolymers are characterized by differential scanning calorimetry (DSC), ¹H‐NMR, FTIR, and gel permeation chromatography (GPC). The thermal properties (T_g) of diblock copolymers depend on polymer compositions. Incorporating larger amount of MCL or BCL into the macromolecular backbone decreases T_g. Their solutions show transparent below a lower critical solution temperature (LCST) and opaque above the LCST. LCST values for the PNIPA‐b‐PMCL aqueous solution were observed to shift to lower temperature than that for PNIPA homopolymers. This work investigates their micellar characteristics in the aqueous phase by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 0.29–2.74 mg L^?1, depending on polymer compositions, which dramatically affect micelle shape. Drug entrapment efficiency and drug loading content of micelles depend on block polymer compositions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of a type of ladder‐like poly(phenyl silsesquioxane) based hybrid star‐shaped copolymer of ε‐caprolactone

Combination of the organic–inorganic hybrid such as silsesquioxane with ε‐caprolactone will lead to materials expected to be environmentally friendly and applicable to biomedical usages. A ladder‐like poly(phenyl silsesquioxane) based hybrid star‐shaped copolymer of ε‐caprolactone was prepared by ring opening polymerization of ε‐caprolactone catalyzed by Sn(Oct)₂ with hydroxyl terminated ladder‐like poly(phenyl silsesquioxane) as initiator. The copolymers were characterized by proton nuclear magnetic resonance (¹H‐NMR), silicon nuclear magnetic resonance (²⁹Si‐NMR), Fourier‐transform infrared spectrometer (FT‐IR), size exclusion chromatography (SEC), thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC) in detail. Furthermore, the enzymatic degradation property of the copolymers was also investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42335.     

Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

The ring‐opening polymerization of ε‐caprolactone initiated with a divalent samarium bis(phosphido) complex [Sm(PPh₂)₂] is reported. The polymerization proceeded under mild reaction conditions and resulted in polyesters with number‐average molecular weights of 8.2 × 10³ to 12.5 × 10³. The yield and molecular weight of poly(ε‐caprolactone)s were dependent on the experimental parameters, such as the monomer/initiator molar ratio, the monomer concentration, the reaction temperature, and the polymerization time. The obtained polymers were characterized with Fourier transform infrared, NMR, gel permeation chromatography, and differential scanning calorimetry. On the basis of an end‐group analysis of low‐molecular‐weight polymers by NMR spectroscopy, a coordination–insertion mechanism is proposed for the polymerization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1558–1564, 2005     

Polymerization of ϵ‐caprolactone initiated through powders of biological and nonbiological glasses

Eight biomedical glasses and three commercial glasses, as finely divided powders, were tested as initiators for the ring‐opening polymerization of ?‐caprolactone in bulk and in vacuo at 185°C. All the glass powders were able to initiate the polymerization, along with Pyrex, which was totally inert toward the monomer as the inner surface of a phial. The obtained polymers were examined with Fourier infrared transform spectroscopy and atomic force microscopy. The molecular weights were measured by viscometry in CHCl₃. The presence of a fraction of the polymer firmly linked to the glass was quantitatively checked by the determination of the weight loss from the residues of the extraction with CHCl₃ after calcination in a kiln at 945°C. The molecular weights and weight losses per unit surface were elaborated mathematically so that a possible correlation between these properties and the atomic compositions of the glasses could be better investigated. Two possible initiation mechanisms, induced by the hydroxyls present on the glass surface, were proposed: one for free poly(?‐caprolactone) and one for poly(?‐caprolactone) linked to the glass. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1579–1586, 2003     

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