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     

Surface chemical analysis of poly(ε‐caprolactone)–perfluoropolyether–poly(ε‐caprolactone) triblock copolymers by X‐ray photoelectron spectroscopy

The air‐side surface composition of a series of poly(ε‐caprolactone)–perfluoropolyether–poly(ε‐caprolactone) triblock copolymers with different compositions and block lengths have been studied by angle‐dependent X‐ray photoelectron spectroscopy (XPS). The weight percentage of the perfluoropolyether (PFPE) and polycaprolactone (PCL) blocks, and ethylene oxide linker (R_H) has been calculated in different ways: from C1s, O1s and F1s photoemission peaks and by line fitting of the C1s and O1s envelopes. The atomic sensitivity factors and the parameters used to fit the peak envelopes have been experimentally determined using some reference materials. A critical discussion of the different methods used in the surface characterization and the degradation of PFPE segments, induced by irradiation beam, have been also reported. A large excess of PFPE with respect to the bulk composition was observed in all samples, and the angular dependence of the XPS signal demonstrated that the content of the fluorinated block segment increased by decreasing the sampling depth. The PFPE surface concentration was also decreased by increasing the PCL/PFPE ratio, but the surfaces of the samples were still dominated by PFPE segments for copolymers with a bulk PFPE composition lower than 10%. Moreover, copolymers with similar PCL/PFPE bulk ratios but with different PFPE block lengths, showed similar PFPE surface composition when the number‐average molecular weight (M_n) was 2000 and 3200 g mol^?1, while that observed for copolymers containing PFPE block with M_n 900 g mol^?1 was lower. Copyright © 2003 Society of Chemical Industry     

Preparation of diblock copolymers consisting of methoxy poly(ethylene glycol) and poly(ε‐caprolactone)/poly(L‐lactide) and their degradation property

Methoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone) (MPEG‐PCL) or MPEG‐b‐poly(L ‐lactide) (MPEG‐PLLA) diblock copolymers were prepared by the polymerization of CL or LA, using MPEG as an initiator in the presence of stannous octoate. MPEG‐b‐poly(ε‐caprolactone‐ran‐L ‐lactide) (MPEG‐PCLA) diblock copolymers with different chemical composition of PCL and PLLA were also prepared by adjusting the amount of CL and LA from MPEG in the presence of stannous octoate. In degradation study, the degradation of the MPEG‐PCLA diblock copolymers mainly depends on the PCL and PLLA segments present in their structure. MPEG‐PCLA, with intermediate ratio of PCL and PLLA segment, completely degraded after 14 weeks. Meanwhile, partially degraded MPEG‐PCLA segments and parent MPEG segments were observed at higher PCL or PLLA segment contents. Introduction of PLLA into the PCL segments caused a lowering of the crystallinity of the diblock copolymers, thus, inducing a faster incoming of water into the copolymers. We confirmed that the diblock copolymers, with lower degree of crystallinity, have degraded more rapidly. POLYM. ENG. SCI., 46: 1242–1249, 2006. © 2006 Society of Plastics Engineers     

AB,BAB and (AB)3 poly(ε‐caprolactone)‐based block copolymers with functionalized poly(meth)acrylate segments

Linear and star‐shaped poly(ε‐caprolactone) (PCL) block copolymers containing poly(meth)acrylate segments with glycidyl, 2‐(trimethylsilyloxy)ethyl and tert‐butyl pendant groups were synthesized using mono‐, di‐ and trifunctional PCL macroinitiators and appropriate (meth)acrylate monomers by controlled radical polymerization. The well‐defined structures with narrow molecular weight distributions indicate the coexistence of semi‐crystalline PCL and amorphous poly(meth)acrylic phases. The hydrophobic nature of the block copolymers can be easily converted to amphiphilic, which with biodegradable and biocompatible PCL segments are promising as polymeric carriers in drug delivery systems. © 2012 Society of Chemical Industry     

Biodegradable poly(vinyl alcohol)‐graft‐ poly(ε‐caprolactone) comb‐like polyester: Microwave synthesis and its characterization

Poly(vinyl alcohol)‐initiated microwave‐assisted ring opening polymerization of ε‐caprolactone in bulk was investigated, and a series of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) (PVA‐g‐PCL) copolymers were prepared, with the degree of polymerization (DP) of PCL side chains and the degree of substitution (DS) of PVA by PCL being in the range of 3–24 and 0.35–0.89, respectively. The resultant comb‐like PVA‐g‐PCL copolymers were confirmed by means of FTIR, ¹H NMR, and viscometry measurement. The introduction of hydrophilic backbone resulted in the decrease in both melting point and crystallization property of the PVA‐g‐PCL copolymers comparing with linear PCL. With higher microwave power, the DP of PCL side chains and DS of PVA backbone were higher, and the polymerization reaction proceeded more rapidly. Both the DP and monomer conversion increased with irradiation time, while the DS increased first and then remained constant. With initiator in low concentration, the DP and DS were higher, while the monomer was converted more slowly. Microwaves dramatically improved the polymerization reaction in comparison of conventional heating method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3973–3979, 2007     

Confined crystallization morphology of poly(ϵ‐caprolactone) block within poly(ϵ‐caprolactone)–poly(l‐lactide) copolymers

The confined crystallization of poly(?‐caprolactone) (PCL) block in poly(?‐caprolactone)–poly(l ‐lactide) (PCL‐PLLA) copolymers was investigated using differential scanning calorimetry, polarized optical microscopy, scanning electronic microscopy and atomic force microscopy. To study the effect of crystallization and molecular chain motion state of PLLA blocks in PCL‐PLLA copolymers on PCL crystallization morphology, high‐temperature annealing (180 °C) and low‐temperature annealing (80 °C) were applied to treat the samples. It was found that the crystallization morphology of PCL block in PCL‐PLLA copolymers is not only related to the ratio of block components, but also related to the thermal history. After annealing PCL‐PLLA copolymers at 180 °C, the molten PCL blocks are rejected from the front of PLLA crystal growth into the amorphous regions, which will lead to PCL and PLLA blocks exhibiting obvious fractionated crystallization and forming various morphologies depending on the length of PLLA segment. On the contrary, PCL blocks more easily form banded spherulites after PCL‐PLLA copolymers are annealed at 80 °C because the preexisting PLLA crystal template and the dangling amorphous PLLA chains on PCL segments more easily cause unequal stresses at opposite fold surfaces of PCL lamellae during the growth process. Also, it was found that the growth rate of banded spherulites is less than that of classical spherulites and the growth rate of banded spherulites decreases with decreasing band spacing. © 2019 Society of Chemical Industry     

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.     

Miscibility of block copolymers of poly(ε‐caprolactone) and poly(ethylene glycol) with poly(3‐hydroxybutyrate) as well as the compatibilizing effect of these copolymers in blends of poly(ε‐caprolactone) and poly(3‐hydroxybutyrate)

Atactic poly(3‐hydroxybutyrate) (a‐PHB) and block copolymers of poly(ethylene glycol) (PEG) with poly(ε‐caprolactone) (PCL‐b‐PEG) were synthesized through anionic polymerization and coordination polymerization, respectively. As demonstrated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) measurements, both chemosynthesized a‐PHB and biosynthesized isotactic PHB (i‐PHB) are miscible with the PEG segment phase of PCL‐b‐PEGs. However, there is no evidence showing miscibility between both PHBs and the PCL segment phase of the copolymer even though PCL has been block‐copolymerized with PEG. Based on these results, PCL‐b‐PEG was added, as a compatibilizer, to both the PCL/a‐PHB blends and the PCL i‐PHB blends. The blend films were obtained through the evaporation of chloroform solutions of mixed components. Excitingly, the improvement in mechanical properties of PCL/PHB blends was achieved as anticipated initially upon the addition of PCL‐b‐PEG. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2600–2608, 2001     

Synthesis,characterization, and hydrolytic degradation of biodegradable poly(ether ester)‐urethane copolymers based on ε‐caprolactone and poly(ethylene glycol)

In this article, a new kind of biodegradable poly(ε‐caprolactone)‐poly(ethylene glycol)‐poly(ε‐caprolactone)‐based polyurethane (PCEC‐U) copolymers were successfully synthesized by melt‐polycondensation method from ε‐caprolactone (ε‐CL), poly(ethylene glycol) (PEG), 1,4‐butanediol (BD), and isophorone diisocyanate (IPDI). The obtained copolymers were characterized by ¹H‐nuclear magnetic resonance (¹H‐NMR), FTIR, and gel permeation chromatography (GPC). Thermal properties of PCEC‐U copolymers were studied by DSC and TGA/DTG under nitrogen atmosphere. Water absorption and hydrolytic degradation behavior of these copolymers were also investigated. Hydrolytic degradation behavior was studied by weight loss method. ¹H‐NMR and GPC were also used to characterize the hydrolytic degradation behavior of PCEC‐U copolymers. The molecular weight of PCL block and PEG block in soft segment and the content of hard segment strongly affected the water absorption and hydrolytic degradation behavior of PCEC‐U copolymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Transesterification in homogeneous poly(ε‐caprolactone)–epoxy blends

Transesterification has been investigated in poly(ε‐caprolactone) (PCL)–epoxy blends. In the hot melt process, the hydroxyl on diglycidyl ether of bisphenol‐A (DGEBA) monomers is too low to give a noticeable transesterification reaction. In the postcure process, model reactions reveal that the hydroxyls from a ring‐opening reaction are able to react with the esters of PCL. In the meantime, the PCL molecular weight decrease and its distribution becomes broader. Nuclear magnetic resonance spectra reveal that fraction of the tertiary hydroxyls converts to secondary hydroxyls. In the cured DGEBA–3,3′‐dimethylmethylene‐di(cyclohexylamine)–PCL blend, a homogeneous morphology is achieved. PCL segments are grafted onto the epoxy network after postcuring and result in the lower T_g observed in the differential scanning calorimetry thermogram. A higher transesterification extent also results in broader transition peaks by dynamic mechanical analysis. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 75–82, 1999     

A statistical study of poly(ε‐caprolactone) crystallinity in poly(ε‐caprolactone)–silica sol–gel materials and their in vitro calcium phosphate‐forming ability

Composite poly(ε‐caprolactone) (PCL)–silica materials for potential use in orthopaedic applications have been prepared by a sol–gel method using an experimental design approach to investigate the effect of synthesis variables, separately and together, on the physical form of the organic polymer. A combination of differential scanning calorimetry, X‐ray diffraction and Fourier‐transform infrared methods were used to obtain information on the arrangement of the organic polymer in the hybrid material. As our studies investigated the effect of synthesis variables simultaneously, it was possible to establish that the increase of tetraethyl orthosilicate (TEOS)/PCL and HCl/TEOS molar ratios decreased the poly(ε‐caprolactone) crystallinity and provided for a better mixing of the two phases. At a mechanistic level it was possible to show that increase in catalyst content affected the condensation of silicon containing species. In vitro calcium phosphate‐forming ability tests using the static biomimetic method have been carried out on selected PCL–silica sol–gels. In vitro bioactivity was only observed for PCL–silica sol–gel composites with high silica content (30% weight). Changes in catalyst levels had a smaller but still significant effect. Calcium phosphate formation on largely non‐porous surfaces is proposed to occur via the formation of a silica sol–gel layer, and is influenced by the topography and the chemistry of the materials surface. Copyright © 2003 Society of Chemical Industry     

Crystallization and melting behavior of poly(ε‐caprolactone‐co‐δ‐valerolactone) and poly(ε‐caprolactone‐co‐L‐lactide) copolymers with novel chain microstructures

Nuclear magnetic resonance spectroscopy (NMR) characterization of the statistical copolymers of this study showed that the poly(ε‐caprolactone‐co‐L‐lactide)s, with ε‐caprolactone (ε‐CL) molar contents ranging from 70 to 94% and ε‐CL average sequence length (l_CL) between 2.20–9.52, and the poly(ε‐caprolactone‐co‐δ‐valerolactone)s, with 60 to 85% of ε‐CL and l_CL between 2.65–6.08, present semi‐alternating (R→2) and random (R～1) distribution of sequences, respectively. These syntheses were carried out with the aim of reducing the crystallinity of poly(ε‐caprolactone) (PCL), needed to provide mechanical strength to the material but also responsible for its slow degradation rate. However, this was not achieved in the case of the ε‐caprolactone‐co‐δ‐valerolactone (ε‐CL‐co‐δ‐VAL). Non‐isothermal cooling treatments at different rates and isothermal crystallizations (at 5, 10, 21 and 37°C) were conducted by differential scanning calorimetry (DSC), and demonstrated that ε‐CL copolymers containing δ‐valerolactone (δ‐VAL) exhibited a larger crystallization capability than those of L‐lactide (L‐LA) and also arranged into crystalline structures over shorter times. The crystallization enthalpies of the ε‐CL‐co‐δ‐VAL copolymers during the cooling treatments and their heat of fusion (ΔH_m) at the different isothermal temperatures were very large (i.e. ΔH_c > 53 Jg^?1) and in some cases, unrelated to the copolymer composition. In some compositions, such as the 60 : 40, Wide Angle X‐ray Scattering (WAXS) proved that that these two lactones undergo isomorphism and co‐crystallize in a single cell. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42534.     

Effect of molecular weight on spherulitic growth rate of poly(ϵ‐caprolactone) and poly(ϵ‐caprolactone)‐b‐poly(ethylene glycol)

The spherulitic growth rates of a series poly (?‐caprolactone) homopolymers and poly(?‐caprolactone)‐b‐ poly(ethylene glycol) (PCL‐b‐PEG) block copolymers with different molecular weights but narrow polydispersity were studied. The results show that for both PCL homopolymers and PCL‐b‐PEG block copolymers, the spherulitic growth rate first increases with molecular weight and reaches a maximum, then decreases as molecular weight increases. Crystallization temperature has greater influence on the spherulitic growth rate of polymers with higher molecular weight. Hoffman–Lauritzen theory was used to analyze spherulitic growth kinetics and the free energy of the folding surface (σ_e) was derived. It is found that the values of σ_e decrease with molecular weight at low molecular weight level and become constant for high molecular weight polymers. The chemically linked PEG block does not change the values of σ_e significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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     

Biodegradable Poly(ε‐Caprolactone)‐Based Graft Copolymers Via Poly(Linoleic Acid): In Vitro Enzymatic Evaluation

Well‐defined graft copolymers based on poly(ε‐caprolactone) (PCL) via poly(linoleic acid) (PLina), are derived from soybean oil. Poly(linoleic acid)‐g‐poly(ε‐caprolactone) (PLina‐g‐PCL) and poly(linoleic acid)‐g‐poly(styrene)‐g‐poly(ε‐caprolactone) (PLina‐g‐PSt‐g‐PCL) were synthesized by ring‐opening polymerization of ε‐caprolactone initiated by PLina and one‐pot synthesis of graft copolymers, and by ring‐opening polymerization and free radical polymerization by using PLina, respectively. PLina‐g‐PCL, PLina‐g‐PSt‐g‐PCL3, and PLina‐g‐PSt‐g‐PCL4 copolymers containing 96.97, 75.04 and 80.34 mol% CL, respectively, have been investigated regarding their enzymatic degradation properties in the presence of Pseudomonas lipase. In terms of weight loss, after 1 month, 51.5 % of PLina‐g‐PCL, 18.8 % of PLina‐g‐PSt‐g‐PCL3, and 38.4 % of PLina‐g‐PSt‐g‐PCL4 were degraded, leaving remaining copolymers with molecular weights of 16,140, 83,220 and 70,600 Da, respectively. Introducing the PLina unit into the copolymers greatly decreased the degradation rate. The molar ratio of [CL]/[Lina] dramatically decreased, from 21.3 to 8.4, after 30 days of incubation. Moreover, reduced PCL content in PLina‐g‐PSt‐g‐PCL copolymers decreased the degradation rate, probably due to the PSt enrichment within the structure, which blocks lipase contact with PCL units. Thus, copolymerization of PCL with PLina and PSt units leads to a controllable degradation profile, which encourages the use of these polymers as promising biomaterials for tissue engineering applications.     

Synthesis and characterization of poly(p‐phenylene)‐graft‐poly(ε‐caprolactone) copolymers by combined ring‐opening polymerization and cross‐coupling processes

2,5‐Dibromo‐1,4‐(dihydroxymethyl)benzene was used as initiator in ring‐opening polymerization of ε‐caprolactone in the presence of stannous octoate (Sn(Oct)₂) catalyst. The resulting poly(ε‐caprolactone) (PCL) macromonomer, with a central 2,5‐dibromo‐1,4‐diphenylene group, was used in combination with 1,4‐dibromo‐2,5‐dimethylbenzene for a Suzuki coupling in the presence of Pd(PPh₃)₄ as catalyst or using the system NiCl₂/bpy/PPh₃/Zn for a Yamamoto‐type polymerization. The poly(p‐phenylenes) (PPP) obtained, with PCL side chains, have solubility properties similar to those of the starting macromonomer, ie soluble in common organic solvents at room temperature. The new polymers were characterized by ¹H and ¹³C NMR and UV spectroscopy and also by GPC measurements. The thermal behaviour of the precursor PCL macromonomer and the final poly(p‐phenylene)‐graft‐poly(ε‐caprolactone) copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry analyses and compared. Copyright © 2004 Society of Chemical Industry     

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     

Biodegradable and photocurable multiblock copolymers with shape‐memory properties from poly(ε‐caprolactone) diol,poly(ethylene glycol), and 5‐cinnamoyloxyisophthalic acid

Biodegradable and photocurable multiblock copolymers of various compositions were synthesized by the high‐temperature solution polycondensation of poly(ε‐caprolactone) (PCL) diols of molecular weight (M_n) = 3000 and poly(ethylene glycol)s (PEG) of M_n = 3000 with a dichloride of 5‐cinnamoyloxyisophthalic acid (ICA) as a chain extender, followed by irradiation by a 400 W high‐pressure mercury lamp (λ > 280 nm) to form a network structure. The gel contents increased with photocuring time, reaching a level of over 90% after 10 min for all copolymers without a photoinitiator. The thermal and mechanical properties of the photocured copolymers were examined by DSC and tensile tests. In cyclic thermomechanical tensile tests, the photocured ICA/PCL/PEG copolymer films showed good shape‐memory properties at 37–60°C, with both shape fixity ratio and shape recovery ratio over 90% at a maximum tensile strain of 100–300%. The water absorption of these copolymers and their rate of degradation in a phosphate buffer solution (pH 7.0) at 37°C increased significantly with increasing PEG content. The novel photocured ICA/PCL/PEG multiblock copolymers are potentially useful in biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Isothermal crystallization kinetics of biodegradable poly(lactic acid)/poly(ε‐caprolactone) blends compatibilized with low‐molecular weight block copolymers

The isothermal crystallization kinetics of biodegradable blends made of poly(lactic acid) (PLA) and poly(ε‐caprolactone) (PCL) compatibilized with two different low molecular weight block copolymers, that is, ε‐caprolactone/tetramethylene ether glycol and ε‐caprolactone/aliphatic polycarbonate (CB), was done. Blends were prepared by melt mixing in an extruder, while isothermal crystallization kinetics and morphologies were investigated by thermal (differential scanning calorimetry) and thermo‐optical (quantitative polarized light optical microscopy [qPLOM]) quantitative methods. Data were analyzed using the Avrami equation, revealing 2D and 3D growth and simultaneous heterogeneous nucleation. The presence of low molecular weight compatibilizers, that is, 2,000 g mol^?1, accelerated the PLA crystallization rate by two to threefold when compared with neat PLA, with high degrees of crystallinity (40–43%) as confirmed by PLOM images. The activation energy (E_a) showed that PCL inhibits PLA crystallization; however, the addition of block copolymers used as compatibilizers of the blends reduced E_a values, increasing the chain mobility of PLA and thus increasing the crystallization rate. POLYM. ENG. SCI., 59:E161–E169, 2019. © 2018 Society of Plastics Engineers     

Nanocomposites based on poly(ϵ‐caprolactone) and the montmorillonite treated with dibutylamine‐terminated ϵ‐caprolactone oligomer

Dibutylamine‐terminated ε‐caprolactone oligomers (CLOs: CLOL, CLOM, and CLOH) with number–averaged molecular weight (M_n), 500, 1300, and 2200, respectively, were synthesized by the ring‐opening polymerization of ε‐caprolactone initiated by 2‐(dibutylamino)ethanol in the presence of tin(II) 2‐ethylhexanoate. Nanocomposites based on poly(ε‐caploractone) (PCL) and the caprolactone oligomer‐treated montmorillonites (CLO‐Ms: CLOL‐M, CLOM‐M, and CLOH‐M) were prepared by melt intercalation method. The XRD and TEM analyses of the PCL composites revealed that the extent of exfoliation of the clay platelets increased with increasing molecular weight of the used CLOs. Tensile strength and modulus of the PCL/CLO‐M composites increased with increasing molecular weight of the CLO and increasing inorganic content. The tensile modulus of the PCL/CLOH‐M nanocomposite with inorganic content 5.0 wt % was three times higher than that of control PCL. Among the PCL/CLO‐M composites, the PCL/CLOM‐M composite had the highest crystallization temperature and melting temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007