Crystallization,melting behavior,and wettability of poly(ε‐caprolactone) and poly(ε‐caprolactone)/ poly(N‐vinylpyrrolidone) blends

Both wettability and crystallizability control poly(ε‐caprolactone)'s (PCL) further applications as biomaterial. The wettability is an important property that is governed by both chemical composition and surface structure. In this study, we prepared the PCL/poly(N‐vinylpyrrolidone) (PVP) blends via successive in situ polymerization steps aiming for improving the wettability and decreasing crystallizability of PCL. The isothermal crystallization of PCL/PVP at different PVP concentrations was carried out. The equilibrium melting point (T), crystallization rate, and the melting behavior after isothermal crystallization were investigated using differential scanning calorimetry (DSC). The Avrami equation was used to fit the isothermal crystallization. The DSC results showed that PVP had restraining effect on the crystallizability of PCL, and the crystallization rate of PCL decreased clearly with the increase of PVP content in the blends. The X‐ray diffraction analysis (WAXD) results agreed with that. Water absorptivity and contact angle tests showed that the hydrophilic properties were improved with the increasing content of PVP in blends. The coefficient for the water diffusion into PCL/PVP blends showed to be non‐Fickian in character. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

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 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     

Synthesis of poly(vinyl alcohol)‐graft‐poly(ε‐caprolactone) and poly(vinyl alcohol)‐graft‐poly(lactide) in melt with magnesium hydride as catalyst

Grafting of poly(ε‐caprolactone) (PCL) and poly(lactide) (PLA) chains on poly(vinyl alcohol) backbone (PVA degree of hydrolysis 99%) was investigated using MgH₂ environmental catalyst and melt‐grown ring‐opening polymerization (ROP) of ε‐caprolactone (CL) and L ‐lactide (LA), that avoiding undesirable toxic catalyst and solvent. The ability of MgH₂ as catalyst as well as yield of reaction were discussed according to various PVA/CL/MgH₂ and PVA/LA/MgH₂ ratio. PVA‐g‐PCL and PVA‐g‐PLA were characterized by ¹H‐ and ¹³C‐NMR, DSC, SEC, IR. For graft copolymers easily soluble in tetrahydrofuran (THF) or chloroform, wettability and surface energy of cast film varied in relation with the length and number of hydrophobic chains. Aqueous solution of micelle‐like particles was realized by dissolution in THF then addition of water. Critical micelle concentration (CMC) decreased with hydrophobic chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Thermoresponsive poly(ϵ‐caprolactone)‐graft‐poly(N‐isopropylacrylamide) graft copolymers prepared by a combination of ring‐opening polymerization and sequential azide–alkyne click chemistry

A straightforward strategy is described to synthesize poly(?‐caprolactone)‐graft‐poly(N‐isopropylacrylamide) (PCL‐g‐PNIPAAm) amphiphilic graft copolymers consisting of potentially biodegradable polyester backbones and thermoresponsive grafting chains. PCL with pendent chlorides was prepared by ring‐opening polymerization, followed by conversion of the pendent chlorides to azides. Alkyne‐terminated PNIPAAm was synthesized by atom transfer radial polymerization. Then, the alkyne end‐functionalized PNIPAAm was grafted onto the PCL backbone by a copper‐catalyzed azide–alkyne cycloaddition. PCL‐g‐PNIPAAm graft copolymers self‐assembled into spherical micelles comprised of PCL cores and PNIPAAm coronas. The critical micelle concentrations of the graft copolymers were in the range 7.8–18.2 mg L^?1, depending on copolymer composition. Mean hydrodynamic diameters of micelles were in the range 65–135 nm, which increased as the length of grafting chains grew. PCL‐g‐PNIPAAm micelles were thermosensitive and aggregated upon heating. © 2014 Society of Chemical Industry     

Synthesis and characterization of biodegradable poly(ester‐urethanes) based on bacterial poly(R‐3‐hydroxybutyrate)

A series of poly(R‐3‐hydroxybutyrate)/poly(ε‐caprolactone)/1,6‐hexamethylene diisocyanate‐segmented poly(ester‐urethanes), having different compositions and different block lengths, were synthesized by one‐step solution polymerization. The molecular weight of poly(R‐3‐hydroxybutyrate)‐diol, PHB‐diol, hard segments was in the range of 2100–4400 and poly(ε‐caprolactone)‐diol, PCL‐diol, soft segments in the range of 1080–5800. The materials obtained were investigated by using differential scanning calorimetry, wide angle X‐ray diffraction and mechanical measurements. All poly(ester‐urethanes) investigated were semicrystalline with T_m varying within 126–148°C. DSC results showed that T_g are shifted to higher temperature with increasing content of PHB hard segments and decreasing molecular weight of PCL soft segments. This indicates partial compatibility of the two phases. In poly(ester‐urethanes) made from PCL soft segments of molecular weight (M_n ≥ 2200), a PCL crystalline phase, in addition to the PHB crystalline phase, was observed. As for the mechanical tensile properties of poly(ester‐urethane) cast films, it was found that the ultimate strength and the elongation at the breakpoint decrease with increasing PHB hard segment content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 703–718, 2002     

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     

Synthesis functional poly(carbonate‐b‐ester) copolymers and micellar characterizations

Functional poly(carbonate‐b‐ester)s were synthesized in buck by ring‐opening polymerization of the carbonate (TMC, MBC, or BMC) with tert‐butyl N‐(2‐hydroxyethyl) carbamate as an initiator, and then with ε‐CL (or ε‐BCL) comonomer. Subsequently, the PMMC‐b‐PCL with pendent carboxyl groups and the PTMC‐b‐PHCL with pendent hydroxyl groups were obtained by catalytic debenzylation. DSC analysis indicated that only one T_g at an intermediate temperature the T_gs of the two polymer blocks. A decrease T_g was observed when an increase contents of ε‐CL incorporated into the copolymers. In contrast, two increased T_ms were observed with increasing PCL content. The block copolymers formed micelle in aqueous phase with critical micelle concentrations (cmcs) in the range of 2.23–14.6 mg/L and with the mean hydrodynamic diameters in the range of 100–280 nm, depending on the composition of copolymers. The drug entrapment efficiency and hydrolytic degradation behavior of micelle were also evaluated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Porous biodegradable polyester blends of poly(L‐lactic acid) and poly(ε‐caprolactone): physical properties,morphology, and biodegradation

Poly(L ‐lactic acid) (PLLA), poly(ε‐caprolactone) (PCL), and their films without or blended with 50 wt% poly(ethylene glycol) (PEG) were prepared by solution casting. Porous films were obtained by water‐extraction of PEG from solution‐cast phase‐separated PLLA‐blend‐PCL‐blend‐PEG films. The effects of PLLA/PCL ratio on the morphology of the porous films and the effects of PLLA/PCL ratio and pores on the physical properties and biodegradability of the films were investigated. The pore size of the blend films decreased with increasing PLLA/PCL ratio. Polymer blending and pore formation gave biodegradable PLLA‐blend‐PCL materials with a wide variety of tensile properties with Young's modulus in the range of 0.07–1.4 GPa and elongation at break in the range 3–380%. Pore formation markedly increased the PLLA crystallinity of porous films, except for low PLLA/PCL ratio. Polymer blending as well as pore formation enhanced the enzymatic degradation of biodegradable polyester blends. Copyright © 2006 Society of Chemical Industry     

A comparative study of poly(l‐lactide)‐block‐poly(ϵ‐caprolactone) six‐armed star diblock copolymers and polylactide/poly(ϵ‐caprolactone) blends

This paper deals with the synthesis of a series of six‐armed star diblock copolymers based on poly(l ‐lactide) (PLLA) and poly(?‐caprolactone) (PCL) by ring‐opening polymerization using stannous octoate as catalyst and the preparation of polylactide (PLA)/PCL linear blends using a solution blending technique, while keeping the PLA‐to‐PCL ratio comparable in both systems. The thermal, rheological and mechanical properties of the copolymers and the blends were comparatively studied. The melting point and the degree of crystallinity were found to be lower for the copolymers than the blends due to poor folding property of star copolymers. Dynamic rheology revealed that the star polymers have lower elastic modulus, storage modulus and viscosity as compared to the corresponding blends with similar composition. The blends show two‐phase dispersed morphology whereas the copolymers exhibited microphase separated morphology with elongated (worm‐like) microdomains. The crystalline structures of the copolymers were characterized by larger crystallites than their blend counterparts, as estimated using Sherrer's equation based on wide‐angle X‐ray diffraction data. © 2016 Society of Chemical Industry     

Esterification on solid support by surface‐initiated ring‐opening polymerization of ε‐caprolactone from benzylic hydroxyl‐functionalized Wang resin bead

Biodegradable poly(ε‐caprolactone) (PCL) was formed on benzylic hydroxyl‐functionalized Wang resin surface by surface‐initiated ring‐opening polymerization (SI‐ROP). The SI‐ROP of ε‐caprolactone was achieved first by treating Wang resin with Tin(II) 2‐ethylhexanoate [Sn(Oct)₂] to form Tin(II) complex, and then followed by polymerization of ε‐caprolactone in anhydrous toluene at 60°C. Thus, the polymer‐grafted Wang resin was characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), optical microscopy (OM), and field‐emission scanning electron microscopy (FE‐SEM). The FTIR spectroscopic analysis of polymer‐grafted Wang resin (Wang‐g‐PCL) reveals the formation of ester linkage between PCL and hydroxyl‐terminated Wang resin. The DSC thermogram shows melting peak corresponding to PCL polymer on Wang resin surface. Thermogravimetric investigation shows increase in PCL content on the Wang resin surface in terms of percentage of weight loss with increase in reaction time. The formation of polymeric layers on the Wang resin surface can be directly visualized from OM and SEM images. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of P(lLA‐co‐εCL) on the compatibility and crystallization behavior of PCL/PLLA blends

This article describes the compatibility of two semicrystalline polymers, poly(ε‐caprolactone) (PCL) and poly(l‐lactic acid) (PLLA). The compatibility of the PCL/PLLA blends was enhanced by the compatibilizing effect of the poly(l,l‐lactide‐co‐ε‐caprolactone) [P(lLA‐co‐εCL)]. A discussion details the effect of the concentration of the compatibilizing agent, the copolymer of l,l‐lactide and ε‐caprolactone of a 50/50 mol ratio [P(lLA‐co‐εCL)], on the compatibility and the crystallization behavior of the blends of PCL and PLLA. It was found that the addition of P(lLA‐co‐εCL) could suppress the crystallization of PLLA at its T_c and induced the concurrent crystallization of PLLA and PCL. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 226–231, 2000     

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     

Part 7. Effects of poly(L‐lactide‐co‐ϵ‐caprolactone) on morphology,structure, crystallization,and physical properties of blends of poly(L‐lactide) and poly(ϵ‐caprolactone)

Blended films of poly(L ‐lactide) [ie poly(L ‐lactic acid)] (PLLA) and poly(?‐caprolactone) (PCL) without or mixed with 10 wt% poly(L ‐lactide‐co‐?‐caprolactone) (PLLA‐CL) were prepared by solution‐casting. The effects of PLLA‐CL on the morphology, phase structure, crystallization, and mechanical properties of films have been investigated using polarization optical microscopy, scanning electron microscopy, differential scanning calorimetry and tensile testing. Addition of PLLA‐CL decreased number densities of spherulites in PLLA and PCL films, and improved the observability of spherulites and the smoothness of cross‐section of the PLLA/PCL blend film. The melting temperatures (T_m) of PLLA and PCL in the films remained unchanged upon addition of PLLA‐CL, while the crystallinities of PLLA and PCL increased at PLLA contents [X_PLLA = weight of PLLA/(weight of PLLA and PCL)] of 0.4–0.7 and at most of the X_PLLA values, respectively. The addition of PLLA‐CL improved the tensile strength and the Young modulus of the films at X_PLLA of 0.5–0.8 and of 0–0.1 and 0.5–0.8, respectively, and the elongation at break of the films at all the X_PLLA values. These findings strongly suggest that PLLA‐CL was miscible with PLLA and PCL, and that the dissolved PLLA‐CL in PLLA‐rich and PCL‐rich phases increased the compatibility between these two phases. © 2003 Society of Chemical Industry     

Enzymatic degradation of blends of poly(ε‐caprolactone) and poly(styrene‐co‐acrylonitrile) by Pseudomonas lipase

In polymer blends, the composition and microcrystalline structure of the blend near surfaces can be markedly different from the bulk properties. In this study, the enzymatic degradation of poly(ε‐caprolactone) (PCL) and its blends with poly(styrene‐co‐acrylonitrile) (SAN) was conducted in a phosphate buffer solution containing Pseudomonas lipase, and the degradation behavior was correlated with the surface properties and crystalline microstructure of the blends. The enzymatic degradation preferentially took place at the amorphous part of PCL film. The melt‐quenched PCL film with low crystallinity and small lamellar thickness showed a higher degradation rate compared with isothermally crystallized (at 36, 40, and 44°C) PCL films. Also, there was a vast difference in the enzymatic degradation behavior of pure PCL and PCL/SAN blends. The pure PCL showed 100% weight loss in a very short time (i.e., 72 h), whereas the PCL/SAN blend containing just 1% SAN showed ～50% weight loss and the degradation ceased, and the blend containing 40% SAN showed almost no weight loss. These results suggest that as degradation proceeds, the nondegradable SAN content increases at the surface of PCL/SAN films and prevents the lipase from attacking the biodegradable PCL chains. This phenomenon was observed even for a very high PCL content in the blend samples. In the blend with low PCL content, the inaccessibility of the amorphous interphase with high SAN content prevented the attack of lipase on the lamellae of PCL. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 868–879, 2002     

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.     

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) as a compatibilizer for cellulose acetate/poly(ε‐caprolactone) blends

Poly(vinyl pyrrolidone‐co‐vinyl acetate)‐graft‐poly(ε‐caprolactone) (PVPVAc‐g‐PCL) was synthesized by radical copolymerization of N‐vinyl‐2‐pyrrolidone (VP)/vinyl acetate (VAc) comonomer and PCL macromonomer containing a reactive 2‐hydroxyethyl methacrylate terminal. The graft copolymer was designed in order to improve the interfacial adhesiveness of an immiscible blend system composed of cellulose acetate/poly(ε‐caprolactone) (CA/PCL). Adequate selections of preparation conditions led to successful acquisition of a series of graft copolymer samples with different values of molecular weight ( ), number of grafts (n), and segmental molecular weight of PVPVAc between adjacent grafts (M_n (between grafts)). Differential scanning calorimetry measurements gave a still immiscible indication for all of the ternary blends of CA/PCL/PVPVAc‐g‐PCL (72 : 18 : 10 in weight) that were prepared by using any of the copolymer samples as a compatibilizer. However, the incorporation enabled the CA/PCL (4 : 1) blend to be easily melt‐molded to give a visually homogeneous film sheet. This compatibilizing effect was found to be drastically enhanced when PVPVAc‐g‐PCLs of higher and M_n (between grafts) and lower n were employed. Scanning electron microscopy revealed that a uniform dispersion of the respective ingredients in the ternary blends was attainable with an assurance of the mixing scale of several hundreds of nanometers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of polyrotaxanes comprising α‐cyclodextrins and poly(ε‐caprolactone) end‐capped with poly(butyl methacrylate)s

Biodegradable polyrotaxane‐based triblock copolymers were synthesized via the bulk atom transfer radical polymerization (ATRP) of n‐butyl methacrylate (BMA) initiated with polypseudo‐rotaxanes (PPRs) built from a distal 2‐bromoisobutyryl end‐capped poly(ε‐caprolactone) (Br‐PCL‐Br) with α‐cyclodextrins (α‐CDs) in the presence of Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine at 45 ºC. The structure was characterized in detail by means of ¹H NMR, gel permeation chromatography, wide‐angle X‐ray diffraction, DSC and TGA. When the feed molar ratio of BMA to Br‐PCL‐Br was changed from 128 to 300, the degree of polymerization of PBMA blocks attached to two ends of the PPRs was in the range 382 ? 803. Although about a tenth of the added α‐CDs were still threaded onto the PCL chain after the ATRP process, the movable α‐CDs made a marked contribution to the mechanical strength enhancement, blood anticoagulation activity and protein adsorption repellency of the resulting copolymers. Meanwhile, they could also protect the copolymers from the attack of H₂O and Lipase AK Amano molecules, exhibiting a lower mass loss as evidenced in hydrolytic and enzymatic degradation experiments. © 2013 Society of Chemical Industry