A biocompatible composite based on poly(ε‐caprolactone fumarate) and hydroxyapatite

Fabrication of biodegradable composites applicable as hard tissue substitutes consisting of poly(ε‐caprolactone fumarate) (PCLF), methacrylic acid (MAA), and hydroxyapatite (HA) was investigated. PCLF macromers were synthesized by reaction of PCL diol with fumaryl chloride in the presence of propylene oxide and characterized by gel permeation chromatography, FTIR, and ¹H NMR spectroscopy. Composites were fabricated by incorporating HA as inorganic filler in PCLF matrix which followed by thermal curing of the composition using benzoyl peroxide and MAA as a free radical initiator and reactive diluent, respectively. Uniform distribution of the fine ceramic phase in the polymer matrix was elucidated by scanning electron microscopy. The effects of the initial macromer molecular weight and the filler volume fraction on mechanical properties and cytotoxicity of the composites were also examined. Significant enhancement in the mechanical properties was observed upon increasing HA content and/or initial PCLF molecular weight. The biocompatibility of the specimens was also improved with increasing ceramic phase. Copyright © 2010 John Wiley & Sons, Ltd.     

Viscoelastic properties of poly(ε‐caprolactone) – hydroxyapatite micro‐ and nano‐composites

Various composites have been proposed in the literature for the fabrication of bioscaffolds for bone tissue engineering. These materials include poly(ε‐caprolactone) (PCL) with hydroxyapatite (HA). Since the biomaterial acts as the medium that transfers mechanical signals from the body to the cells, the fundamental properties of the biomaterials should be characterized. Furthermore, in order to control the processing of these materials into scaffolds, the characterization of the fundamental properties is also necessary. In this study, the physical, thermal, mechanical, and viscoelastic properties of the PCL‐HA micro‐ and nano‐composites were characterized. Although the addition of filler particles increased the compressive modulus by up to 450%, the thermal and viscoelastic properties were unaffected. Furthermore, although the presence of water plasticized the polymer, the viscoelastic behavior was only minimally affected. Testing the composites under various conditions showed that the addition of HA can strengthen PCL without changing its viscoelastic response. The results found in this study can be used to further understand and approximate the time‐dependent behavior of scaffolds for bone tissue engineering. Copyright © 2012 John Wiley & Sons, Ltd.     

Crystallization behavior of poly(ε‐caprolactone)/multiwalled carbon nanotube composites

Differential scanning calorimetry (DSC), polarized optical microscopy, and X‐ray diffraction methods were used to investigate the isothermal crystallization behavior and crystalline structure of poly(?‐caprolactone) (PCL)/multiwalled carbon nanotube (MWNT) composites. PCL/MWNT composites were prepared via the mixing of a PCL polymer solution with carboxylic groups containing multiwalled carbon nanotubes (c‐MWNTs). Both Raman and Fourier transform infrared spectra indicated that carboxylic acid groups formed at both ends and on the sidewalls of the MWNTs. A transmission electron microscopy micrograph showed that c‐MWNTs were well separated and uniformly distributed in the PCL matrix. DSC isothermal results revealed that introducing c‐MWNTs into the PCL structure caused strongly heterogeneous nucleation induced by a change in the crystal growth process. The activation energy of PCL drastically decreased with the presence of 0.25 wt % c‐MWNT in PCL/c‐MWNT composites and then increased with increasing MWNT content. The result indicated that the addition of c‐MWNT to PCL induced heterogeneous nucleation (lower total activation energy) at a lower c‐MWNT content and then reduced the transportation ability of polymer chains during crystallization processes at a higher MWNT content (higher total activation energy). A correlation between the crystallization kinetics, melting behavior, and crystalline structure of PCL/c‐MWNT composites was also discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 598–606, 2006     

Polyurethane elastomers based on amphiphilic poly(caprolactone)‐b‐poly(butadiene)‐b‐poly(caprolactone) triblockcopolyols

Hydroxyl‐terminated poly(butadiene) (HTPB; M_n = 2100 g mol⁻¹) was capped with 30 and 60 wt % of ɛ‐caprolactone to reach amphiphilic triblock copolymers in form of capped poly(butadiene) CPB. The former (CPB30; M_n = 3300 g/mol) is amorphous with a glass temperature of −56 °C. CPB60 (M_n = 4000 g mol⁻¹) is semi‐crystalline with a melting point of 50 °C and a glass transition at −47 °C. The CPBs, HTPB and polycaprolactone diol (M_n = 2000 g mol⁻¹) were used as soft segment components in the preparation of polyurethane elastomers (PUE), using a 1/1 mixture of an MDI prepolymer and uretonimine modified MDI, and hard phase components in form of 1,3‐propane diol, 1,4‐butane diol, and 1,5‐pentane diol. CPB‐based elastomers with 1,4 butane diol (8 wt %) show hard domains as fringed aggregates with a better connection to the continuous phase than the HTPB‐based PUE. The soft segment glass transition temperature (T_g) is at −28 °C for HTPB‐based PUE and at −43 °C for those of CPB. The tensile strength of the CPB30&60‐based PUE is found between 20 and 30 MPa at an elongation at break of 400% and 550%, respectively. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1162–1172     

Development of Electrospun Three‐arm Star Poly(ε‐caprolactone) Meshes for Tissue Engineering Applications

We have developed three‐dimensional electrospun microfibrous meshes of a novel star branched three‐arm poly(ε‐caprolactone) (*PCL) as potential scaffolds for tissue engineering applications. The processing conditions required to obtain uniform fibers were optimized by studying their influence on fiber morphology and size. Polymer molecular weight and solution feed rate influenced both the mesh microstructure and the tensile properties of the developed mats. Electrospun samples were also tested for their mechanical properties in wet conditions, showing higher yield strength and strain in comparison to that observed in dry conditions. Cell culture experiments employing MC3T3‐E1 osteoblast like cells showed good cell viability adhesion and collagen production on the *PCL scaffolds.

     

Physical properties of poly(ε‐caprolactone) layered silicate nanocomposites prepared by controlled grafting polymerization

Poly(ε‐caprolactone) (PCL) chains grafted onto montmorillonite modified by a mixture of nonfunctional ammonium salts and ammonium‐bearing hydroxyl groups were prepared. The clay content was fixed to 3 wt %, whereas the hydroxyl functionality was 25, 50, 75, and 100%, obtaining an intercalated or exfoliated system. The transport properties of water and dichloromethane vapors and the mechanical properties were investigated. The mechanical and dynamic mechanical analyses showed improvement of the nanocomposite elastic modulus in a wide temperature range. Interestingly, for the higher hydroxyl contents (50, 75, and 100%), the decrease of modulus at higher temperature, due to the PCL crystalline melting, did not lead to the loss of mechanical consistence of the samples. Consequently, they revealed a measurable modulus up to 120 °C, a much higher temperature with respect to pure PCL. Water sorption was investigated in the entire activity range, and a lower sorption was observed on increasing the hydroxyl content, up to the sample with 100% hydroxyl content, which turned to be completely impermeable, even in liquid water. The sample with 75% hydroxyl content showed a threshold activity (a = 0.4) below which it was impermeable to water vapor. Also, the diffusion parameters decreased when the hydroxyl content increased, up to the 100% sample, which showed zero diffusion. The diffusion parameters of an organic vapor, dichloromethane, also exhibited a decreasing value on increasing the hydroxyl content in the nanocomposites. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1466–1475, 2004     

Mechanical,thermal and morphological properties of poly(ε‐caprolactone)/zein blends

Blends of poly(ε‐caprolactone) (PCL) with zein (PCL/zein) in different proportions (100/0, 75/25, 50/50, 25/75 and 0/100 wt% containing 5 wt% glycerol) were compared based on their mechanical properties (tensile strength, elongation at break, and Young's modulus), and on their thermal properties, the latter determined by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The morphology of the materials was studied by scanning electron microscopy (SEM). Blends of PCL/zein showed reduced tensile strength and elongation at break, but increased Young's modulus compared to the pure polymers, in agreement with the DMTA and SEM results. These findings indicated that PCL and zein were incompatible. TGA showed that the thermal stability was enhanced by the addition of zein to PCL, whereas SEM showed a poor interfacial interaction between the polymers. Copyright © 2004 John Wiley & Sons, Ltd.     

Nonisothermal crystallization kinetics of poly(ε‐caprolactone) blocks in double crystalline triblock copolymers containing poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and poly(ε‐caprolactone) units

The poly(3‐hydroxbutyrate‐co‐3‐hydroxyvalerate)/poly(ε‐caprolactone) block copolymers (PHCLs) with three different weight ratios of PCL blocks (38%, named PHCL‐38; 53%, named PHCL‐53; and 60%, named PHCL‐60) were synthesized by using PHBV with two hydroxyl end groups to initiate ring‐opening polymerization of ε‐caprolactone. During DSC cooling process, melt crystallization of PHCL‐53 at relatively high cooling rates (9, 12, and 15 °C min^?1) and PHCL‐60 at all the selected cooling rates corresponded to PCL blocks so that PHCL‐53 and PHCL‐60 were used to study the nonisothermal crystallization behaviors of PCL blocks. The kinetics of PCL blocks in PHCL‐53 and PHCL‐60 under nonisothermal crystallization conditions were analyzed by Mo equation. Mo equation was successful in describing the nonisothermal crystallization kinetics of PCL blocks in PHCLs. Crystallization activation energy were estimated using Kissinger's method. The results of kinetic parameters showed that both blocks crystallized more difficultly than corresponding homopolymers. With the increase of PCL content, the crystallization rate of PCL block increased gradually. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Microwave syntheses of poly(ε‐caprolactam‐co‐ε‐caprolactone)

Microwave irradiation was applied to synthesize poly(ε‐caprolactam‐co‐ε‐caprolactone) directly from the anionic catalyzed ring opening of two cyclic monomers, ε‐caprolactam and ε‐caprolactone using a variable frequency microwave furnace, programmed to a set temperature and controlled by a pulsed power on–off system. Dielectric properties of ε‐caprolactam, ε‐caprolactone, and their mixture were measured in the microwave range from 0.4 to 3 GHz, showing that both ε‐caprolactam and ε‐caprolactone exhibited effective absorption of microwave energy to induce a fast chemical reaction. The microwave induced anionic copolymerization of ε‐caprolactam and ε‐caprolactone generated copoly(amide‐ester)s in yields as high as 70%. Conventional thermal and microwave copolymerization studies were also conducted for comparison with the microwave results. These studies demonstrated that an effective and efficient microwave method to copolymerize ε‐caprolactam with ε‐caprolactone in higher yield, higher amide content, and higher T_g 's, relative to the thermal process, has been developed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1379–1390, 2000     

Synthesis and characterization of poly(β‐hydroxybutyrate) and poly(ϵ‐caprolactone) copolyester by transesterification

To synthesize the copolyester of poly(β‐hydroxybutyrate) (PHB) and poly(?‐caprolactone) (PCL), the transesterification of PHB and PCL was carried out in the liquid phase with stannous octoate as the catalyzer. The effects of reaction conditions on the transesterification, including catalyzer concentration, reaction temperature, and reaction time, were investigated. The results showed that both rising reaction temperature and increasing reaction time were advantageous to the transesterification. The sequence distribution, thermal behavior, and thermal stability of the copolyesters were investigated by ¹³C NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, optical microscopy, and thermogravimetric analysis. The transesterification of PHB and PCL was confirmed to produce the block copolymers. With an increasing PCL content in the copolyesters, the thermal behavior of the copolyesters changed evidently. However, the introduction of PCL segments into PHB chains did not affect its crystalline structure. Moreover, thermal stability of the copolyesters was little improved in air as compared with that of pure PHB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1893–1903, 2002     

Fibrillar structure of resorbable microblock copolymers based on 1,5‐dioxepan‐2‐one and ε‐caprolactone

The copolymerization of 1,5‐dioxepan‐2‐one (DXO) and ε‐caprolactone, initiated by a five‐membered cyclic tin alkoxide initiator, was performed in chloroform at 60 °C. Copolymers with different molar ratios of DXO (25, 40, and 60%) were synthesized and characterized. ¹³C NMR spectroscopy of the carbonyl region revealed the formation of copolymers with a blocklike structure. Differential scanning calorimetry measurements showed that all the copolymers had a single glass transition between ?57 and ?49 °C and a melting temperature in the range of 30.1–47.7 °C, both of which were correlated with the amount of DXO. An increase in the amount of DXO led to an increase in the glass‐transition temperature and to a decrease in the melting temperature. Dynamic mechanical thermal analysis measurements confirmed the results of the calorimetric analysis, showing a single sharp drop in the storage modulus in the temperature region corresponding to the glass transition. Tensile testing demonstrated good mechanical properties with a tensile strength of 27–39 MPa and an elongation at break of up to 1400%. The morphology of the copolymers was examined with polarized optical microscopy and atomic force microscopy; the films that crystallized from the melt showed a short fibrillar structure (with a length of 0.05–0.4 μm) in contrast to the untreated solution‐cast films. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2412–2423, 2003     

Controlling the mechanical properties of poly(L‐lactide– ε‐caprolactone) monofilament sutures by an acetone/water treatment

For monofilament biodegradable sutures fabricated from the L ‐lactide–ε‐caprolactone (75/25) copolymer [P(LLA/CL)], there have been some concerns regarding their mechanical properties, such as the knot‐pull strength and stiffness. This article demonstrates the further potentiality of these sutures through improvements in those properties. With the aim of diminishing the molecular orientation, particularly in the suture surface region, we adopted an expedient method to treat P(LLA/CL) sutures with an acetone/water mixture, using different times and time patterns. The changes in the molecular orientation distributions across the suture cross sections were characterized by the specific index of birefringence measured with an interference microscope. The crystal orientations, knot‐pull strengths, tensile strengths, and bending rigidity were measured. The conformational changes in suture breaking during knot‐pull tests were analyzed with high‐speed‐video observations. Morphological analyses of the fractural surfaces were performed with scanning electron microscopy. The knot‐pull strength tended to rise, in comparison with that of untreated samples, up to a certain treatment time and was accompanied by a minimal decrement of the tensile strength. The knot‐pull strength did not show an increasing trend with further treatment, whereas the tensile strength declined remarkably. The birefringence, crystal orientation, bending rigidity, fractured surface analysis, and high‐speed‐video observations revealed molecular disorientation mainly in the filament outer layers for that particular treatment causing the sutures to be considerably softer. The suture softness played a role in changing the deformation behavior of the knot when a load was applied and caused the knot‐pull strength to rise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2449–2462, 2002     

Grafting of poly(ε‐caprolactone) onto maghemite nanoparticles

We report the coating of maghemite (γ‐Fe₂O₃) nanoparticles with poly(ε‐caprolactone) (PCL) through a covalent grafting to technique. ω‐Hydroxy‐PCL was first synthesized by the ring‐opening polymerization of ε‐caprolactone with aluminum isopropoxide and benzyl alcohol as a catalytic system. The hydroxy end groups of PCL were then derivatized with 3‐isocyanatopropyltriethoxysilane in the presence of tetraoctyltin. The triethoxysilane‐functionalized PCL macromolecules were finally allowed to react on the surface of maghemite nanoparticles. The composite nanoparticles were characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Effects of the polymer molar mass and concentration on the amount of polymer grafted to the surface were investigated. Typical grafting densities up to 3 μmol of polymer chains per m² of maghemite surface were obtained with this grafting to technique. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6011–6020, 2004     

Supramolecular inclusion complexation of polyhedral oligomeric silsesquioxane capped poly(ε‐caprolactone) with α‐cyclodextrin

Supramolecular inclusion complexes (ICs) involving polyhedral oligomeric silsesquioxane (POSS) capped poly(?‐caprolactone) (PCL) and α‐cyclodextrin (α‐CD) were investigated. POSS‐terminated PCLs with various molecular weights were prepared via the ring‐opening polymerization of ?‐caprolactone (CL) with 3‐hydroxypropylheptaphenyl POSS as an initiator. Because of the presence of the bulky silsesquioxane terminal group, the inclusion complexation between α‐CD and the POSS‐capped PCL was carried out only with a single end of a PCL chain threading inside the cavity of α‐CD, which allowed the evaluation of the effect of the POSS terminal groups on the efficiency of the inclusion complexation. The X‐ray diffraction results indicated that the organic–inorganic ICs had a channel‐type crystalline structure. The stoichiometry of the organic–inorganic ICs was quite dependent on the molecular weights of the POSS‐capped PCLs. With moderate molecular weights of the POSS‐capped PCLs (e.g., M_n =3860 or 9880), the stoichiometry was 1:1 mol/mol (CL unit/α‐CD), which was close to the literature value based on the inclusion complexation of α‐CD with normal linear PCL chains with comparable molecular weights. When the PCL chains were shorter (e.g., for the POSS‐capped PCL of M_n = 1720 or 2490), the efficiency of the inclusion complexation decreased. The decreased efficiency of the inclusion complexation could be attributed to the lower mobility of the bulky POSS group, which restricted the motion of the PCL chain attached to the silsesquioxane cage. This effect was pronounced with the decreasing length of the PCL chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1247–1259, 2007     

Synthesis and properties of photocurable biodegradable multiblock copolymers based on poly(ε‐caprolactone) and poly(L‐lactide) segments

Photocurable biodegradable multiblock copolymers were synthesized from poly(ε‐caprolactone) (PCL) diol and poly(L ‐lactide) (PLLA) diol with 4,4′‐(adipoyldioxy)dicinnamic acid (CAC) dichloride as a chain extender derived from adipoyl chloride and 4‐hydroxycinnamic acid, and they were characterized with Fourier transform infrared and ¹H NMR spectroscopy, gel permeation chromatography, wide‐angle X‐ray diffraction, differential scanning calorimetry, and tensile tests. The copolymers were irradiated with a 400‐W high‐pressure mercury lamp from 30 min to 3 h to form a network structure in the absence of photoinitiators. The gel concentration increased with time, and a concentration of approximately 90% was obtained in 90–180 min for all the films. The photocuring hardly affected the crystallinity and melting temperature of the PCL segments but reduced the crystallinity of the PLLA segments. The mechanical properties, such as the tensile strength, modulus, and elongation, were significantly affected by the copolymer compositions and gel concentrations. Shape‐memory properties were determined with cyclic thermomechanical experiments. The CAC/PCL and CAC/PCL/PLLA (75/25) films photocured for 30–120 min showed good shape‐memory properties with strain fixity rates and recovery rates of approximately 100%. The formation of the network structure and the crystallization and melting of the PCL segments played very important roles for the typical shape‐memory properties. Finally, the degradation characteristics of these copolymers were investigated in a phosphate buffer solution at 37 °C with proteinase‐k and Pseudomonas cepacia lipase. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2426–2439, 2005     

Segmental dynamics in poly(ε‐caprolactone)/poly(L‐lactide) copolymer networks

Poly(ε‐caprolactone) (PCL) and poly(lactic acid) (PLA) networks were prepared from macromonomer diols functionalized with methacrylic anhydride, which allows one to get self‐crosslinkable polymers. Besides, both macromonomers were copolymerized to get copolymer networks with different compositions (namely, PCL/PLA: 0/100, 70/30, 50/50, 30/70, 100/0). Dielectric and calorimetric experiments allow one to conclude the microphase separation of the system: one phase made of pure PCL domains while the second one consists of caprolactone units, which somehow plasticize PLA and moves its main relaxation (glass transition) to lower temperatures. The effect of crosslinking PLA on the dynamics of the system was further investigated by comparing with the dynamics for linear PLA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 183–193, 2009     

Deformation behavior of electrospun poly(L‐lactide‐co‐ε‐caprolactone) nonwoven membranes under uniaxial tensile loading

Biodegradable poly(L ‐lactide‐co‐ε‐caprolactone) copolymers with different L ‐lactide (LLA)/ε‐caprolactone (CL) ratios of 75/25 and 50/50 were electrospun into fine fibers. The deformation behavior of the electrospun membranes with randomly oriented structures was evaluated under uniaxial tensile loading. The electrospun membrane with a higher LLA content showed a significantly higher tensile modulus but a similar maximum stress and a lower ultimate strain in comparison with the membrane with a lower LLA content. The beaded fibers that formed in the membranes caused lower tensile properties. X‐ray diffraction and differential scanning calorimetry results suggested that the electrospun fine fibers developed highly oriented structures in CL‐unit sequences during the electrospinning process even though the concentration was only 25 wt %. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3205–3212, 2005     

Synthesis and characterization of photocrosslinked poly(ε‐caprolactone)s showing shape‐memory properties

Poly(ε‐caprolactone) (PCL) with a pendent coumarin group was prepared by solution polycondensation from 7‐(3,5‐dicarboxyphenyl) carbonylmethoxycoumarin dichloride and α, ω‐dihydroxy terminated poly(ε‐caprolactone) with molecular weights of 1250, 3000, and 10,000 g/mol. These photosensitive polymers underwent a rapid reversible photocrosslinking upon exposure to irradiation with alternating wavelengths (>280/254 nm) without a photoinitiator. The thermal and mechanical properties of the photocrosslinked films were examined by means of differential scanning calorimetry and stress–strain measurements. The crosslinked films exhibited elastic properties above the melting temperature of the PCL segment along with significant decrease in the ultimate tensile strength and Young's modulus. Shape‐memory properties such as strain fixity ratio (R_f) and strain recovery ratio (R_r) were determined by means of a cyclic thermomechanical tensile experiments under varying maximum strains (ε_m = 100, 300, and 500%). The crosslinked ICM/PCL‐3000 and ‐10,000 films exhibited the excellent shape‐memory properties in which both R_f and R_r values were 88–100% for tensile strain of 100–500%; after the deformation, the films recovered their permanent shapes instantaneously. In vitro degradation was performed in a phosphate buffer saline (pH 7.2) at 37 °C with or without the presence of Pseudomonas cepacia lipase. The presence of the pendent coumarin group and the crosslinking of the polymers pronouncedly decreased the degradation rate. The crosslinked biodegradable PCL showing a good shape‐memory property is promising as a new material for biomedical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2422–2433, 2009     

Synthesis of linear and star‐like poly(ε‐caprolactone)‐b‐poly{γ‐2‐[2‐(2‐methoxy‐ethoxy)ethoxy]ethoxy‐ε‐caprolactone} amphiphilic block copolymers using zinc undecylenate

Linear and star‐like amphiphilic diblock copolymers were synthesized by the ring‐opening polymerization of ε‐caprolactone and γ‐2‐[2‐(2‐methoxyethoxy)ethoxy]ethoxy‐ε‐caprolactone monomers using zinc undecylenate as a catalyst. These polymers have potential applications as micellar drug delivery vehicles, therefore the properties of the linear and 4‐arm star‐like structures were examined in terms of their molecular weight, viscosity, thermodynamic stability, size, morphology, and drug loading capacity. Both the star‐like and linear block copolymers showed good thermodynamic stability and degradability. However, the star‐like polymers were shown to have increased stability at lower concentrations with a critical micelle concentration (CMC) of 5.62 × 10^?4 g L^?1, which is less than half the concentration of linear polymer needed to form micelles. The star‐like polymeric micelles showed smaller sizes when compared with their linear counterparts and a higher drug loading capacity of doxorubicin, making them better suited for drug delivery purposes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3601–3608     

Pendant groups fine‐tuning thermal gelation of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) aqueous solution

Novel poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) (PCL‐PEG‐PCL) bearing pendant hydrophobic γ‐(carbamic acid benzyl ester) groups (PECB) and hydrophiphilic amino groups (PECN) were synthesized based on the functionalized comonomer γ‐(carbamic acid benzyl ester)‐ε‐caprolactone (CABCL). The thermal gelation behavior of the amphiphilic copolymer aqueous solutions was examined. The phase transition behavior could be finely tuned via the pendant groups, and an abnormal phenomenon occurred that the sol–gel transition temperature shifted to a higher temperature for PECB whereas a lower temperature for PECN. The micelles percolation was adopted to clarify the hydrogel mechanism, and the effect of the pendant groups on the micellization was further investigated in detail. The results demonstrated that the introduction of γ‐(carbamic acid benzyl ester) pendant groups significantly decreased the crystallinity of the copolymer micelles whereas amino pendant groups made the micelles easy to aggregate. Thus, the thermal gelation of PEG/PCL aqueous solution could be finely tuned by the pendant groups, and the pendant groups modified PEG/PCL hydrogels are expected to have great potential biomedical application. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2571–2581