Polymerization Of CL Research Articles

Synthesis of poly(N-isopropylacrylamide)-b-poly(ɛ-caprolactone) and its inclusion compound of β-cyclodextrin

Well-defined amphiphilic poly(N-isopropylacrylamide)-b-poly(ɛ-caprolactone) (PNIPAM-b-PCL) block copolymers have been successfully prepared in two steps. PNIPAMOH is firstly prepared by using 4,4′-azobis(4-cyano-1-pentanol) as bifunctional initiator, and then PNIPAM-b-PCL copolymer is synthesized via a ring-opening polymerization of CL using PNIPAMOH as a macro-initiator in the presence of stannous octoate as a catalyst. The PNIPAM-b-PCL copolymers self-assemble to form spherical micelles of 50–130nm in diameter, which can be modulated by the chain length of PCL block. The inclusion complexes are fabricated by treating PNIPAM-b-PCL with β-cyclodextrin and they are characterized by infrared and 1H NMR spectroscopies, X-ray powder diffraction, thermogravimetric analysis, and differential scanning calorimetry.

Amphiphilic star‐shaped poly(ε‐caprolactone)‐block‐poly(l‐lysine) copolymers with porphyrin core: Synthesis, self‐assembly, and cell viability assay

AbstractStar‐shaped copolymers poly(ε‐caprolactone)‐bolck‐poly(ε‐benzyloxycarbonyl‐l‐lysine) (SPPCL‐b‐PZLLs) with porphyrin core were synthesized by a sequential ring‐opening polymerization (ROP) of CL and Nε‐Benzyloxycarbonyl‐l‐lysine N‐Carboxyanhydride. After the deprotection of benzyloxycarbonyl groups in polylysine blocks, the star‐shaped amphiphilic copolymers SPPCL‐b‐PLLs were obtained. These amphiphilic copolymers can self‐assemble into micelles or aggregates in aqueous solution. Investigation shows that the morphology of micelles/aggregates varied according to the change of pH values of media, indicating the pH‐responsive property of SPPCL‐b‐PLL copolymers. Furthermore, associated with conjugated porphyrin cores, the SPPCL‐b‐PLL copolymers micelles showed a certain degree of Photodynamic Therapy (PDT) effects on tumor cells, suggesting its potential application as carrier for hydrophobic drug with additional therapeutic ability of inherent porphyrin segments. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40097.

Tough polyamide 6/core–shell blends prepared via in situ anionic polymerization of ε‐caprolactam by reactive extrusion

In this study, the molten ε‐caprolactam (CL) solution of maleated styrene‐ethylene/butylene‐styrene block copolymer (SEBS‐g‐MA) and polystyrene (PS) containing catalyst and activator were introduced into a twin screw extruder, and polyamide 6 (PA6)/SEBS/PS blends were successfully prepared via anionic polymerization of CL by reactive extrusion. The mechanical properties measurements indicated that both the elongation at break and notched Izod impact strength of PA6/SEBS/PS (85/10/5) blends were improved distinctly with slight loss of tensile and flexural strength as compared to that of pure PA6. The images of transmission electron microscopy showed that a core–shell structure with PS core and poly (ethene‐co‐1‐butene) (PEB) shell was formed within the PA6 matrix. Fourier transform infrared was used to investigate the formation mechanisms of the core–shell structure. POLYM. ENG. SCI., 53:2705–2710, 2013. © 2013 Society of Plastics Engineers

Biodegradable cross-linked poly(trimethylene carbonate) networks for implant applications: Synthesis and properties

In order to avoid the deformation of poly(trimethylene carbonate) (PTMC) in vivo applications, bis(cyclic carbonate) was synthesized and used as cross-linker to prepare PTMC based biodegradable networks via ring-opening polymerization of TMC and/or CL with stannous octanoate as catalyst. The effect of the cross-linking on the resulted networks was studied. The results showed that the crosslinker had high reactivity and efficiency to form stable polymeric networks with high gel percentage, high decomposition temperature and good mechanical properties. These obtained networks were amorphous and elastic, and the glass transition temperatures were below physiological temperature (37 °C), which were expected to be rubbery for in vivo applications. The properties of the networks could be predictably controlled and tailed by varying the polymer composition and cross-linker amount in feed. The cross-linked PTMC based networks showed a potential biomedical application of loading drugs for implanted devices.

The Ring‐Opening Polymerization of ε‐Caprolactone Catalyzed by Molybdenum Trioxide: A Kinetic Approach Study Using NMR and DSC Data

AbstractThe bulk ring‐opening polymerization (ROP) of ε‐caprolactone (CL), catalyzed by molybdenum trioxide (α‐MoO3), was investigated under nitrogen atmosphere at 150°C. Effect of monomer/initiator ([CL]0/[I]0, I = MoO3) and monomer/initiator/co‐initiator ([CL]0/[I]0/[CoI]0, CoI = ROH and H2O) ratios on monomer conversion and molecular weight were determined. Bulk polymerization of CL was completed within 20 hours at 150°C for [CL]0/[I]0 = 100. Propagation was first order in CL concentration and initiator at this temperature, being the rate constant of propagation kp equal to 2.27 × 10−4 mol−1 l s−1. Polymerization reaction was accelerated by the addition of small amounts of water and n‐octanol. In the presence of water (up to [CL]0/[H2O]0 = 120), polymerization rate increases and was completed within 6 hours at 150°C; for higher amounts of water (150 to 180), lower conversions are observed. However, control of number‐average molecular weight was only efficient for [CL]0/[H2O]0 = 20 and 30. In the presence of n‐octanol, degradation of polyester occurs at early stages of polymerization. Kinetic data for polymerization (obtained by 1H‐NMR) were fitted to 14 different model reaction functions. It was found that a linear model represents better the conversion versus time plots for bulk polymerization, in agreement with the pseudo living nature of polymerization.

Acid and reduction dually cleavable amphiphilic comb-like copolymer micelles for controlled drug delivery

Disulfide- and acetal-functionalized comb-like copolymers (SACP) with poly(ε-caprolactone) (PCL) and poly(ethylene glycol) (PEG) side chains and a polymethacrylate backbone were synthesized and self-assembled for in vitro encapsulation and release of an anticancer drug, doxorubicin (DOX). Three step reactions including RAFT copolymerization of 2-hydroxyethyl methacrylate and poly(ethylene glycol) methyl ether methacrylate mediated by a disulfide-functionalized RAFT agent, hydroxyl-vinyloxy addition reaction to introduce acid cleavable PEG segments, and CL polymerization to grow PCL chains were used to generate the target dual-sensitive comb-like copolymers. Meanwhile, well-defined normal comb-like polymers (CP), acid-cleavable comb-like polymers (ACP) and disulfide-linked comb-like polymers (SCP) with PEG and PCL pendent chains were also prepared and acted as analogues of SACP. All the resultant comb-like copolymers had the desired chemical structures, well-controlled molecular weight and relatively low polydispersity (PDI = 1.09–1.16), evident from 1H NMR and GPC-MALLS analyses. DLS and TEM measurements revealed that these copolymers were liable to self-assemble into micelles or large compound micelles in aqueous solution, and SACP aggregates could be dissociated and reaggregated in the presence of acidic PBS solution (pH 5.0) or 10 mM DL-dithiothreitol (DTT). Compared with CP aggregates with a lack of cleavable linkage, ACP, SCP and SACP aggregates upon acid and reduction stimuli could quickly release the encapsulated DOX, and the cumulative release from SACP aggregates could be roughly adjusted by addition of a single stimulus or dual stimuli. These results confirmed their great potential as novel nanocarriers and delivery systems.

Improving the ring-opening polymerization of ε-caprolactone and l-lactide using stannous octanoate

A series of ligands were tested to meliorate the catalytic activity of e-caprolactone (CL) and l-lactide (LA) polymerization by Sn(Oct)2 and BnOH. There are seven ligands (methyl 2-(dibenzylamino)acetate (MDBAA), di(1H-pyrazol-1-yl)methane, benzanide, 8-aminoquinoline, 2-bromo-1-phenylethanone, 2,6-di-tert-butyl-4-methylphenol, and dipyridine) were found to be useful in increasing the polymerization rate for CL polymerization. For LA polymerization, there are only two ligands (8-aminoquinoline and p-thiocresol) effectively raised the polymerization rate. Moreover, the kinetic study reveals a first-order dependency on [CL] and second-order dependency on [LA], indicating different polymerization mechanisms in Sn(Oct)2 catalytic system. The mechanistic study also explains that MDBAA could potentially modify the framework of the catalytic intermediate and produce the hydrogen, thereby increasing the rate of CL polymerization.

Unsymmetrical N-Heterocyclic Carbene: 1-Isopropyl-3-benzylimidazol-2-ylidene as Catalyst for Ring-Opening Polymerization of ϵ-Caprolactone

An unsymmetrical N-heterocyclic carbene, namely 1-isopropyl-3-benzylimidazol-2-ylidene, is a highly active catalyst for ring-opening polymerization of ϵ-caprolactone (CL) to give polycaprolactone (PCL) with number average molecular weight (Mn) as high as 2.66 × 104 at 0°C in 100 min in tetrahydrofuran (THF). The effects of monomer/initiator molar ratio ([M]/[I]), catalyst/initiator molar ratio ([C]/[I]), monomer concentration, as well as polymerization temperature and time have been investigated. The kinetic studies of CL polymerization have indicated that the polymerization rate is first-order with respect to both monomer and catalyst concentrations. The apparent activation energy amounts to 56.04 kJ/mol. The proposed mechanism is a monomer-activated process.

ε-Caprolactone polymerization under air by the biocatalyst: Magnesium 2,6-di-tert-butyl-4-methylphenoxide

This study investigated the synthesis of the biocatalyst, magnesium 2,6-di-tert-butyl-4-methylphenoxide (Mg(BHT)2) complex, and the ring-opening polymerization (ROP) of ε-caprolactone (CL). The complex demonstrates high catalytic activity and controllable of molecular weight for the ROP of CL in tetrahydrofuran at room temperature, even when polymerization was performed under air. Before this study, the polymerization of CL had never been performed using a magnesium catalyst under air at room temperature. Various forms of alcohols with different purposes were also used as initiators with Mg(BHT)2. The results show that the magnesium complex acts as a perfect catalyst because of its high catalytic activity and control ability without any cytotoxicity in the polymerization of CL, making it suitable for biomedical applications. In addition, nanoparticle formation, cytotoxicity, and phototoxicity of tri-2-hydroxyethyl ester [Ce6-(CH2CH2OPCL)3] were also studied in this article and Ce6-(CH2CH2OPCL)3 formed nanoparticle can act as a nanophotosensitizer for photodynamic therapy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Random copolymers based on trimethylene carbonate and ε‐caprolactone for implant applications: Synthesis and properties

AbstractRandom copolymers of trimethylene carbonate (TMC) and ε‐caprolactone (CL) have been synthesized by ring‐opening polymerization of TMC and CL in the presence of stannous octoate. The effects of feeding dose, reaction temperature and polymerization time, and effect of catalyst content on the copolymerization were investigated. The results showed that the composition of the copolymers was in good agreement with the feeding dose, and the molecular weight of the copolymers decreased firstly with increasing CL content and then increased. The decrease in the reaction temperature, polymerization time and catalyst content would increase the molecular weight of the copolymers. Furthermore, the feeding dose affected the thermal and mechanical properties of the copolymer largely, and the possessing different properties of random copolymers could be obtained by adjusting the copolymer compositions. This work could optimize the polymerization conditions to achieve the copolymers with controlled properties for implant applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Simple Route to Size-Tunable Degradable and Electroactive Nanoparticles from the Self-Assembly of Conducting Coil–Rod–Coil Triblock Copolymers

A simple route to size-tunable nanoparticles from the self-assembly of degradable and electrically conductive coil–rod–coil triblock copolymers based on an aliphatic polyester and conducting species is presented. A series of coil–rod–coil triblock copolymers consisting of a middle aniline pentamer (AP) segment and two polycaprolactone (PCL) segments were easily synthesized by a combination of a ring-opening polymerization of CL initiated by an aniline dimer (AD) giving AD-PCL and an oxidative coupling reaction between the AD-PCL and p-phenylenediamine. This strategy avoids the multistep reaction used in previous work. The electroactivity of these copolymers was investigated by UV and cyclic voltammetry. The conductivity of the copolymers was dependent on the AP content and the conductivity mechanism of the triblock copolymers is discussed. Interestingly, these triblock copolymers can undergo self-assembly in selective solvent such as CHCl3 as indicated by NMR and transmission electron microscope (TEM) obs...

Poly(<i>Ethylene Oxide</i>)-B-Poly(<i>ε-Caprolactone</i>) Amphiphilic Block Copolymers: Synthesis and Self-Assembly

A series of amphiphilic block copolymers mPEO-b-PCL with different PCL molecular weight were successfully prepared by combination of anionic ring-opening polymerization with coordination-insertion ring-opening polymerization. Firstly, the linear mPEO was prepared by anionic ring-opening copolymerization of EO with 2-(2-methoxyethoxy) ethoxide potassium as the small molecule initiators, then the mPEO as the macroinitiator was used to initiate the ring-opening polymerization of CL, in the absence of Sn(Oct)2 as the catalyst, and amphiphilic block copolymers mPEO-b-PCL were obtained. By changing the ratio of monomer and macroinitiator, prepared a series of different molecular weight mPEO-b-PCL. The structure of intermediates and final products were characterized by 1H NMR and GPC. The critical micelle concentration (cmc) of the final copolymer was measured. In addition, the sizes and morphologies of the obtained micelles at different PCL chains were studied with Laser nano-particle size analyzer and transmission electron microscopy (TEM).

Fine Tuning Micellar Core-Forming Block of Poly(ethylene glycol)-block-poly(ε-caprolactone) Amphiphilic Copolymers Based on Chemical Modification for the Solubilization and Delivery of Doxorubicin

This study aimed to optimize poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-b-PCL)-based amphiphilic block copolymers for achieving a better micellar drug delivery system (DDS) with improved solubilization and delivery of doxorubicin (DOX). First, the Flory-Huggins interaction parameters between DOX and the core-forming segments [i.e., poly(ε-caprolactone) (PCL) and poly[(ε-caprolactone-co-γ-(carbamic acid benzyl ester)-ε-caprolactone] (P(CL-co-CABCL))] was calculated to assess the drug-polymer compatibility. The results indicated a better compatibility between DOX and P(CL-co-CABCL) than that between DOX and PCL, motivating the synthesis of monomethoxy-poly(ethylene glycol)-b-poly[(ε-caprolactone-co-γ-(carbamic acid benzyl ester)-ε-caprolactone] (mPEG-b-P(CL-co-CABCL)) block copolymer. Second, two novel block copolymers of mPEG-b-P(CL-co-CABCL) with different compositions were prepared via ring-opening polymerization of CL and CABCL using mPEG as a macroinitiator and characterized by (1)H NMR, FT-IR, GPC, WAXD, and DSC techniques. It was found that the introduction of CABCL decreased the crystallinity of mPEG-b-PCL copolymer. Micellar formation of the copolymers in aqueous solution was investigated with fluorescence spectroscopy, DLS and TEM. mPEG-b-P(CL-co-CABCL) copolymers had a lower critical micelle concentration (CMC) than mPEG-b-PCL and subsequently led to an improved stability of prepared micelles. Furthermore, both higher loading capacity and slower in vitro release of DOX were observed for micelles of copolymers with increased content of CABCL, attributed to both improved drug-core compatibility and favorable amorphous core structure. Meanwhile, DOX-loaded micelles facilitated better uptake of DOX by HepG2 cells and were mainly retained in the cytosol, whereas free DOX accumulated more in the nuclei. However, possibly because of the slower intracellular release of DOX, DOX-loaded micelles were less potent in inhibiting cell proliferation than free DOX in vitro. Taken together, the introduction of CABCL in the core-forming block of mPEG-b-PCL resulted in micelles with superior properties, which hold great promise for drug delivery applications.

Conversion of sulfuric acid lignin generated during bioethanol production from lignocellulosic materials into polyesters with ɛ-caprolactone

In this study, polyesters were prepared from sulfuric acid lignin (SAL) that was generated as a by-product during the production of bioethanol from lignocellulosic materials using ɛ-caprolactone (CL). Carboxylic groups were introduced into SAL by a hydrothermal reaction under alkali conditions. The acid form (-COOH) of the obtained polymer (HSAL) was dissolved into ɛ-caprolactone and the mixture was heated at 150°C for 12 h with ZnCl2 as a catalyst. The structure of the obtained polymer (PCL-HSAL) was proposed based on results of differential scanning calorimetric analysis, swelling tests, and dynamic mechanical thermal analysis. The hydroxyl group in HSAL participated in the ring-opening polymerization of CL. PCL-HSAL with a high HSAL content formed a three-dimensional network that did not dissolve in organic solvents and did not melt at high temperature. PCL-HSAL showed a high swelling property for a suitable ratio of CL to HSAL.

Ring-opening polymerization of ɛ-caprolactone by poly(propyleneglycol) in the presence of a monomer activator

The ring-opening polymerization of ɛ-caprolactone (CL) was induced by using polypropylene glycol (PPG) as an initiator in the presence of the monomer activator HCl·Et 2O to synthesize triblock copolymers composed of PPG and poly(ɛ-caprolactone) (PCL). The degree of CL conversion and the molecular weight of PCL increased linearly with the polymerization time or with the feed ratio of CL to PPG in the presence of HCl·Et 2O in CH 2Cl 2 at 25 °C. The PCLs obtained had molecular weights close to the theoretical values calculated from the CL:PPG molar ratios and exhibited monomodal GPC curves with narrow polydispersity indexes. The apparent rate constant ( k app) for the polymerization of CL activated by HCl·Et 2O was greatly affected by the ratio of HCl·Et 2O/PPG. The activation energy for the polymerization of CL in this system was estimated to be 49.8 kJ/mol K. We successfully prepared PPG and PCL triblock copolymers using this activated monomer mechanism.

Aluminum Complexes with Bidentate N,N‐Dialkylaniline–arylamido Ligands: Synthesis, Structures, and Catalytic Properties for Efficient Ring‐Opening Polymerization of ϵ‐Caprolactone

AbstractA number of Al complexes bearing bidentate N,N‐dialkylaniline–arylamido ligands, ortho‐(ArNCH2)C6H4NR2AlMe2 (R = Me, Ar = 2,6‐iPr2C6H3, 3a; 2,6‐Et2C6H3, 3b; 2,6‐Me2C6H3, 3c; 4‐MeC6H4, 3d; Ph, 3e; and R = Et, Ar = 2,6‐iPr2C6H3, 3f; 2,6‐Me2C6H3, 3g; Ph, 3h), have been synthesized from the reaction of the corresponding free ligands, ortho‐(ArNHCH2)C6H4NR2 (R = Me, Ar = 2,6‐iPr2C6H3, 2a; 2,6‐Et2C6H3, 2b; 2,6‐Me2C6H3, 2c; 4‐MeC6H4, 2d; Ph, 2e; and R = Et, Ar = 2,6‐iPr2C6H3, 2f; 2,6‐Me2C6H3, 2g; Ph, 2h), with AlMe3 (1 equiv.). All complexes were characterized by 1H and 13C NMR spectroscopy and elemental analysis. Single‐crystal X‐ray diffraction analysis of complexes 3c and 3e revealed that these Al complexes have a distorted tetrahedral geometry around the metal center. All complexes were found to be efficient catalysts for the ring‐opening polymerization of ϵ‐caprolactone (CL) in the presence of benzyl alcohol, and complexes 3a–h catalyze the polymerization of CL in a living fashion. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

An innovative method to improve the electrical conductivity of multi-walled carbon nanotubes filled polyamide 6/polystyrene blends

An innovative method has been successfully developed to improve the electrical conductivity of polyamide 6/polystyrene (PA6/PS) blends in this paper. PA6/PS blends containing multi-walled carbon nanotubes (MWCNTs) are prepared by the radical polymerization of styrene in the presence of є-caprolactam (CL) and MWCNTs, followed by the in-situ anionic ring-opening polymerization of CL. In the resulted PA6/PS blends, MWCNTs are selectively located at the interface of PA6 and PS. Because the interface of 0.5 and 1.0 wt.% MWCNTs filled blends with PA6/PS weight ratio of 70/30 is continuous, a MWCNTs conductive pathway is formed in these two blends, which results in a decrease of volume resistivity by about 9 orders of magnitude.

One‐pot synthesis of linear‐hyperbranched diblock copolymers via self‐condensing vinyl polymerization and ring opening polymerization

AbstractThe linear poly(ε–caprolacton)‐b‐hyperbrached poly(2‐((α‐bromobutyryl)oxy)ethyl acrylate) (LPCL‐b‐HPBBEA) has been successfully synthesized by simultaneous ring‐opening polymerization (ROP) of CL and self‐condensing vinyl polymerization (SCVP) of BBEA in one‐pot. The HPBBEA homopolymers were found to be formed in the polymerization because of the competitive reactions induced by initiation with bifunctional initiator, 2‐hydroxylethyl‐2′‐bromoisobutyrate (HEBiB), and inimer BBEA. The separation of LPCL‐b‐HPBBEA from the polymerization products was achieved by precipitation in methanol. With feed ratio increase of CL and BBEA to HEBiB, the molecular weights of PCL and HPBBEA blocks in the block copolymer enhanced; and the polymerization rate of CL started to decrease gradually after 12 h of polymerization, but the polymerization rate of BBEA was maintained until 24 h of polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7628–7636, 2008

Surface modification of starch nanocrystals through ring‐opening polymerization of ε‐caprolactone and investigation of their microstructures

AbstractBionanoparticles of starch obtained by submitting native potato starch granules to acid hydrolysis conditions. The resulted starch nanoparticles were used as core or macro initiator for polymerization of ε‐caprolactone (CL). Starch nanoparticle‐g‐polycaprolactone was synthesized through ring‐opening polymerization (ROP) of CL in the presence of Sn(Oct)2 as initiator. The detailed microstructure of the resulted copolymer was characterized with NMR spectroscopy. Thermal characteristic of the copolymer was investigated using DSC and TGA. By introducing PCL, the range of melting temperature for starch was increased and degradation of copolymer occurred in a broader region. X‐ray diffraction and TEM micrographs confirmed that there was no alteration of starch crystalline structure and morphology of nanoparticles, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Synthesis of adaptative and amphiphilic polymer model conetworks by versatile combination of ATRP, ROP, and “Click chemistry”

Well-defined adaptative and amphiphilic polymer conetworks based on hydrophilic poly(N,N-dimethylamino-2-ethyl methacrylate) (PDMAEMA) and hydrophobic poly(e-caprolactone) (PCL) have been prepared by combination of ATRP, ROP, and Click chemistry. Telechelic α,ω-alkyne terminated PCL crosslinker was obtained by ring-opening polymerization (ROP) of CL in THF at 80 °C initiated by 1,4-butanediol and catalyzed by tin(II) bis 2-ethyl hexanoate (Sn(Oct) 2 ), followed by the quantitative esterification of hydroxyl end-groups by activated 4-pentynoic acid. In parallel, an azido-containing PDMAEMA-based copolymer was obtained in a three-step strategy involving primarily the copolymerization of DMAEMA with newly synthesized 2-(2-azidoethoxy)ethyl methacrylate (AEEMA) monomer. The latter was obtained by nucleophilic substitution of chloride atom from 2-(2-chloroethoxy)ethanol by an azide group followed by the esterification reaction of the hydroxyl group with methacrylic anhydride. The copolymerization was carried out in an equivolumic mixture of H 2 O and isopropanol at r.t. and initiated by a ω-bromoisobutyryl oligo PEO macroinitiator in the presence of various ligated copper(I)-based catalysts. In a last step, both polymer precursors were chemically linked by the Huisgen-1,3-dipolar cycloaddition in anhydrous THF at r.t. using CuBr complexed by 2,2'-bipyridine ligand as catalyst. Final material was characterized by the means of DSC and SEM, both attesting of a homogeneous distribution of the PCL crosslinkers and a highly porous structure in this new amphiphilic model conetworks.