Direct grafting of ε‐caprolactone on solid core/mesoporous shell silica spheres by surface‐initiated ring‐opening polymerization

Poly(?‐caprolactone) (PCL) was formed on Solid core/mesoporous shell (SCMS) silica surface by surface‐initiated ring‐opening polymerization (SI‐ROP). The SI‐ROP of ?‐caprolactone was achieved by heating a mixture of SCMS silica, ?‐caprolactone and the tin(II) 2‐ethylhexanoate [Sn(Oct)₂] in a anhydrous toluene for 20 h at different temperatures viz. 40, 60, and 80°C. The PCL grafted SCMS silica was characterized by fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X‐ray, differential scanning calorimetry and scanning electron microscopy (SEM). The FTIR spectroscopic analysis reveals the formation of ester linkage between PCL and hydroxyl terminated SCMS silica. TGA investigation shows increase in PCL content on SCMS silica surface with increase in reaction temperature. The SEM photographs clearly show the formation of PCL polymer on the SCMS silica surface without altering the spherical nature of SCMS silica. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surface‐initiated ring‐opening polymerization of ϵ‐caprolactone from the surface of PP film

This article presents the ring‐opening polymerization of ε‐caprolactone (ε‐CL) from PP film modified with an initiator layer composed of ? OSn(Oct) groups. This method consists of two steps: (1) Sn(Oct)₂ exchanged with the hydroxyl groups on the surface of PP film, forming the ? OSn(Oct) groups bonded on the surface; (2) surface‐initiated ring‐opening polymerization of ε‐CL with the ? OSn(Oct) groups. The initiator layer is characterized by attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR), contact angles, and X‐ray photoelectron spectroscopy (XPS). The growth of PCL chains from the initiator layer through ring‐opening polymerization is successfully achieved. ATR‐FTIR, XPS, and scanning electron microscope (SEM) are also used to characterize the grafted film. XPS results reveal that the PCL chains cover the surface of PP film after 4 h. The SEM images reveal that the PCL chain clusters grow into regular spheroidal particles, which can be changed into other different morphology by treated with different solvents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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     

Morphological,thermal, and mechanical properties of poly(ε‐caprolactone)/poly(ε‐caprolactone)‐grafted‐cellulose nanocrystals mats produced by electrospinning

Electrospun nanocomposites of poly(ε‐caprolactone) (PCL) incorporated with PCL‐grafted cellulose nanocrystals (PCL‐g‐CNC) were produced. PCL chains were grafted from cellulose nanocrystals (CNC) surface by ring‐opening polymerization. Grafting was confirmed by infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA). The resulting PCL‐g‐CNC were then incorporated into a PCL matrix at various loadings. Homogeneous nanofibers with average diameter decreasing with the addition of PCL‐g‐CNC were observed by scanning electron microscopy (SEM). PCL‐g‐CNC domains incorporated into the PCL matrix were visualized by transmission electron microscopy (TEM). Thermal and mechanical properties of the mats were analyzed by differential scanning calorimetry (DSC), TGA and dynamic mechanical analysis (DMA). The addition of PCL‐g‐CNC into the PCL matrix caused changes in the thermal behavior and crystallinity of the electrospun fibers. Significant improvements in Young's modulus and in strain at break with increasing PCL‐g‐CNC loadings were found. These results highlighted the great potential of cellulose nanocrystals as a reinforcement phase in electrospun PCL mats, which can be used as biomedical materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43445.     

Synthesis of poly(ε‐caprolactone)/clay nanocomposites using polyhedral oligomeric silsesquioxane surfactants as organic modifier and initiator

Poly(ε‐caprolactone)/clay nanocomposites were synthesized by in situ ring‐opening polymerization of ε‐caprolactone in the presence of montmorillonite modified by hydroxyl functionalized, quaternized polyhedral oligomeric silsesquioxane (POSS) surfactants. The octa(3‐chloropropyl) polyhedral oligomeric silsesquioxane was prepared by hydrolytic condensation of 3‐chloropropyltrimethoxysilane, which was subsequently quaternized with 2‐dimethylaminoethanol. Montmorillonite was modified with the quaternized surfactants by cation exchange reaction. Bulk polymerization of ε‐caprolactone was conducted at 110°C using stannous octoate as an initiator/catalyst. Nanocomposites were analyzed by X‐ray diffraction, transmission electron microscopy, thermo gravimetric analysis, and differential scanning calorimetry. Hydroxyl functionalized POSS was employed as a surface modifier for clay which gives stable clay separation for its 3‐D structure and also facilitates the miscibility of polymer with clay in the nanocomposites due to the star architecture. An improvement in the thermal stability of PCL was observed even at 1 wt % of clay loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Novel biodegradable amphiphilic poly(ε‐caprolactone)/poly(N‐vinylpyrrolidone) blends via successive in situ polymerizations

In this study, biodegradable blends of poly(ε‐caprolactone) (PCL) and poly(N‐vinylpyrrolidone) (PVP) were prepared by a new strategy in the following steps: (1) free radical polymerization of N‐vinyl‐2‐pyrrolidone (NVP) in ε‐caprolactone (CL); (2) ring‐opening polymerization of ε‐caprolactone in the presence of PVP to obtain the target blends. The structure of the blends was confirmed by FTIR and ¹H NMR, and the molecular weight of PCL and PVP were determined by GPC. SEM study revealed that this polymerization method could decrease the disperse phase size and improve the interphase when compared with solution‐blending method. The phase inversion occurred when PVP content was 15–20 wt %. Subsequently, the PCL sphere dispersed in PVP matrix and its size decreased with the increase of PVP content. The contact angle results showed that PVP has a profound effect on hydrophilic properties of PCL/PVP blends. PCL/PVP blends are believed to be promising for drug delivery, cell therapy, and other biomedical applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Miscibility windows in ternary polymer blends of a polyester,polymethacrylate and poly(styrene‐co‐acrylonitrile)

Miscibility, phase diagrams and morphology of poly(ε‐caprolactone) (PCL)/poly(benzyl methacrylate) (PBzMA)/poly(styrene‐co‐acrylonitrile) (SAN) ternary blends were investigated by differential scanning calorimetry (DSC), optical microscopy (OM), and scanning electron microscopy (SEM). The miscibility window of PCL/PBzMA/SAN ternary blends is influenced by the acrylonitrile (AN) content in the SAN copolymers. At ambient temperature, the ternary polymer blend is completely miscible within a closed‐loop miscibility window. DSC showed only one glass transition temperature (T_g) for PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 ternary blends; furthermore, OM and SEM results showed that PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 were homogeneous for any composition of the ternary phase diagram. Hence, it demonstrated that miscibility exists for PCL/PBzMA/SAN‐17 and PCL/PBzMA/SAN‐25 ternary blends, but that the ternary system becomes phase‐separated outside these AN contents. Copyright © 2003 Society of Chemical Industry     

Functionalization of multi‐walled carbon nanotubes with poly(ε‐caprolactone) using click chemistry

Multi‐walled carbon nanotubes (MWNTs) were covalently functionalized with poly(ε‐caprolactone) (PCL) using click chemistry. First, chlorine moiety‐containing PCL was synthesized by the copolymerization of α‐chloro‐ε‐caprolactone with ε‐caprolactone monomer using ring opening polymerization, and further converted to azide moiety‐containing PCL. The alkyne‐functionalized MWNTs were prepared with the treatment of p‐amino propargyl ether using a solvent free diazotization procedure. The covalent functionalization of alkyne‐derived MWNTs with azide moiety‐containing PCL was accomplished using Cu(I)‐catalyzed [3+2] Huisgen dipolar cycloaddition click chemistry. The PCL‐functionalization of MWNTs was confirmed by the measurements of Fourier transform infra‐red, NMR, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal and mechanical properties of semi‐interpenetrating polymer networks composed of diisocyanate‐bridged,four‐armed,star‐shaped ε‐caprolactone oligomers and poly(ε‐caprolactone)

Semi‐interpenetrating polymer networks (S‐IPNs) were prepared by the reactions of hydroxyl‐terminated four‐armed, star‐shaped ε‐caprolactone oligomers with degrees of polymerization per one oligocaprolactone chain (ns) of 3, 5, and 10 and 2,4‐tolylene diisocyanate (TDI) in the presence of poly(ε‐caprolactone) (PCL). In the dynamic mechanical analysis of the S‐IPN [2,4‐tolylene diisocyanate bridged hydroxyl‐terminated four‐armed, star‐shaped ε‐caprolactone oligomer (TH4CLO)/PCL], only one tan δ peak was observed; its temperature increased with increasing TH4CLO content and with decreasing n value. Differential scanning calorimetric analyses of the TH4CLOs and TH4CLO/PCLs revealed that the TH4CLOs with ns of 3 and 5 were amorphous, whereas TH4CLO with an n of 10 was semicrystalline and that the crystallization of the PCL chain for TH4CLO/PCLs was more strongly disturbed with increasing TH4CLO content and decreasing n value. Although the tensile strength, modulus, and elongation at break of TH4CLO were much lower than those of PCL, those values increased with the n value. Although the tensile strength and modulus of the TH4CLO/PCLs decreased with increasing TH4CLO content, TH4CLO (n = 3)/PCL 50/50 showed the highest elongation at break (314%) among the S‐IPNs because of the suppression of crystallization of the polycaprolactone chain. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4229–4236, 2013     

Microheterogeneous polymer systems prepared by suspension polymerization of methyl methacrylate in the presence of poly(ε‐caprolactone)

Poly(methyl methacrylate) – polycaprolactone (PMMA/PCL) microheterogeneous beads were synthesized by suspension polymerization starting from methyl methacrylate (MMA) monomer and PCL, which was synthesized by ring‐opening polymerization of ε‐caprolactone using ZnCl₂ as initiator. The resulting polymer was fully characterized by ¹H and ¹³C NMR, differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and dynamic mechanical thermal analysis (DMTA). The size distribution and morphology of the resulting beads were investigated by optical microscopy and scanning electron microscopy (SEM). Moreover, blends of PMMA beads and PCL in different proportions were prepared and the morphology of the films was examined by optical microscopy. The low compatibility between PMMA and PCL was clearly evidenced through these experiments.     

Cyclohexene oxide mid‐chain functional macromonomer of poly(ε‐caprolactone): Synthesis,characterization, and photoinitiated cationic homo‐ and copolymerization

In this study, a novel well‐defined epoxy mid‐chain functional macromonomer of poly(ε‐caprolactone) (PCL) has been synthesized by ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) and epoxidation on workup with 3‐chloroperoxybenzoic acid. The ROP of ε‐CL monomer in bulk at 110°C, by means of a dihydroxy functional initiator namely, 3‐cyclohexene‐1,1‐dimethanol in conjunction with stannous‐2‐ethylhexanoate, (Sn(Oct)₂), yielded a well‐defined PCL with a cyclohexene mid‐chain group. The epoxidation of the cyclohexene (CH) mid‐chain group of PCL was performed using 3‐chloroperoxybenzoic acid. GPC, IR, and ¹H‐NMR analyses revealed that a low‐polydispersity macromonomer of PCL with the desired cyclohexene oxide (CHO) functionality at the mid‐chain was obtained. The photoinduced cationic polymerizations of this macromonomer yielded comb‐shaped and graft copolymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characterization and electrical properties of honeycomb‐patterned poly(ε‐caprolactone)/reduced graphene oxide composite film

A novel biocompatible composite of poly(ε‐caprolactone) (PCL) was synthesized via in situ ring‐opening polymerization method of ε‐caprolactone in the presence of reduced graphene oxide (RGO). Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS) studies support a strong interaction between PCL and RGO. The crystallization behavior and thermal stability of these composites were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Honeycomb‐patterned thin films with regular structures were fabricated by casting the composite solution under humid conditions. The temperature‐dependent DC conductivity of the honeycomb‐patterned composite films was studied in the range of 290−330 K, which revealed a semiconducting behavior in the transport properties of the composite films. DC conductivity of the patterned films was increased by increasing the concentration of RGO in the composites and in the increased temperature. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

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     

Synthesis and characterization of amphiphilic hydroxypropylcellulose‐graft‐poly(ε‐caprolactone)

An amphiphilic graft copolymer, hydroxypropylcellulose‐graft‐poly(ε‐caprolactone) (HPC‐g‐PCL), was synthesized by bulk polymerization without a catalyst and characterized with one‐dimensional and two‐dimensional NMR spectroscopy. Molar substitution of ε‐caprolactone on HPC (MS_CL) was estimated by both gravimetry and ¹H‐NMR, and the gravimetric method was considered suitable for MS_CL determination. Heterogeneity in the HPC‐g‐PCL film was suggested by a microscopic study, and the existence of PCL‐rich crystalline regions was confirmed by the results of X‐ray diffraction and differential scanning calorimetry (DSC). The double endotherm observed in the DSC scans of HPC‐g‐PCL was associated with the different molecular weight fractions in the copolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 718–727, 2003     

Preparation and conductive properties of polycaprolactone‐grafted carbon black nanocomposites

Polycaprolactone‐grafted carbon black (CB‐g‐PCL) nanocomposites were prepared by surface‐initiated ring‐opening polymerization of ε‐caprolactone on the surface of CB. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscope (AFM), X‐ray diffraction (XRD), and polarizing optical microscope (POM) method were employed to characterize the resultant CB‐g‐PCL. The effect of temperature on resistivity of polycaprolactone‐grafted CB (CB‐g‐PCL) nanocomposites was investigated and compared with that of mixture of CB and PCL. It was found that CB‐g‐PCL nanocomposites exhibited positive temperature coefficient (PTC) phenomena between 48 and 51°C, and negative temperature coefficient (NTC) phenomena and between 51 and 54°C. The prepared CB‐g‐PCL nanocomposites have the potential to be temperature‐dependent switch materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structure and properties of new thermoforming bionanocomposites based on chitin whisker‐graft‐polycaprolactone

Thermoformable bionanocomposites of chitin whisker‐graft‐polycaprolactone (CHW‐g‐PCL) were synthesized by initiating the ring‐opening polymerization of caprolactone monomer onto the CHW surface under microwave radiation. In this case, the “graft from” strategy contributed to long and dense “plasticizing” PCL tails onto the CHW surface as the key of thermoforming, and, therefore, such bionanocomposites were injection‐molded as the sheets with a structure of cocontinuous phase mediated with the entanglement of grafted PCL chains. The structure and properties of the molded CHW‐g‐PCL sheets were investigated by FTIR, XRD, SEM, DSC, DMTA, contact angle measurement, and tensile test. With an increase of the PCL content in CHW‐g‐PCL, the strength and elongation as well as the hydrophobicity of the nanocomposites increased at one time. This is the first report on the thermoformable polymer‐grafted nanocrystal derived from natural polysaccharide. Moreover, such new bionanocomposites with good mechanical performances could have great potential applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Paper‐sheet biocomposites based on wood pulp grafted with poly(ε‐caprolactone)

Kraft pulp fibers were used as substrates for the grafting of poly(ε‐caprolactone) (PCL) from available hydroxyl groups through ring‐opening polymerization, targeting three different chain lengths (degree of polymerization): 120, 240, and 480. In a paper‐making process, paper‐sheet biocomposites composed of grafted fibers and neat pulp fibers were prepared. The paper sheets possessed both the appearance and the tactility of ordinary paper sheets. Additionally, the sheets were homogenous, suggesting that PCL‐grafted fibers and neat fibers were compatible, as demonstrated by both Fourier transform infrared spectroscopy microscopy and through dye‐labeling of the PCL‐grafted fibers. Finally, it was shown that the paper‐sheet biocomposites could be hot‐pressed into laminate structures without the addition of any matrix polymer; the adhesive joint produced could even be stronger than the papers themselves. This apparent and sufficient adhesion between the layers was thought to be due to chain entanglements and/or co‐crystallization of adjacent grafted PCL chains within the different paper sheets. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42039.     

In‐depth characterization of granular starch‐graft‐polyester compositions as obtained by in situ polymerization of lactones from the starch surface

The synthesis of poly(ε‐caprolactone) (PCL)‐grafted granular starch was carried out either in bulk (without solvent) or in toluene suspension by a two‐step procedure. First step relied upon the activation of the hydroxyl groups available at the starch surface by alkylaluminum derivatives like AlEt₃ and removal of non‐surface‐grafted organo‐aluminum active species. The latter species were made free in solution by reaction with the remaining water molecules still contaminating the polymerization medium despite intensive drying of the starch granules. In the second step, ε‐caprolactone was polymerized via a coordination‐insertion ring‐opening polymerization as initiated by the surface‐grafted aluminum alkoxide species. The present contribution aims at investigating various parameters such as nature of the alkyl aluminum activator and monomer (δ‐valerolactone was studied as well), temperature, concentration, and addition of a solvent (polymerization in toluene suspension), reaction time, and also the experimental procedure used to recover the polyester chains and measure the grafting efficiency. It turns out that, under the studied conditions, dialkylaluminum alkoxides surface‐grafted onto the starch granules were more likely generated and promote a fast polymerization reaction with the formation of grafted PCL chains with a molecular weight that can be as high as 225 000 (M_n value) for polymerization carried out in toluene suspension. Copyright © 2004 Society of Chemical Industry     

Comparative study of the thermal and mechanical properties of nanocomposites prepared by in situ polymerization of ε‐caprolactone and functionalized carbon nanotubes

As an effort to compare the influence of several types of functionalized carbon nanotubes (CNTs) upon the mechanical and thermal properties of nanocomposites prepared with a poly(ε‐caprolactone) (PCL) as matrix and functionalized CNTs as fillers; nanocomposites of PCL–CNTs were studied in this study. CNTs were synthesized by chemical vapor deposition using dry ethanol as the carbon source. High resolution scanning electron microscopy, high resolution transmission electron microscopy, and Raman and infrared spectroscopies were used to characterize the CNTs obtained. Four chemical synthesis routes were exploited to add different types of chemical groups onto the surface of purified CNTs. Specifically, the authors inserted: (i) N‐methylpyrrolidine, (ii) carboxyl and hydroxyl, (iii) urethane, and (iv) phenylmethanol groups onto CNTs surface. Nanocomposites were synthesized by in situ polymerization of ε‐caprolactone (ε‐CL) in presence of 1 wt% of each type of functionalized CNTs. Young's moduli of the nanocomposites prepared with N‐methylpyrrolidine or carboxyl and hydroxyl functionalized CNTs are higher than the one of pure PCL, whereas all the mechanical properties of the nanocomposites containing urethane or phenylmethanol groups evaluated at the break point were higher than those of pure PCL. Thermal stability of all the nanocomposites studied improved with respect to pure PCL. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers