Synthesis and self-assembly of a new amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(ε-caprolactone) block copolymer

New amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(ε-caprolactone) (PNVCL-b-PCL) block copolymers were synthesized by ring-opening polymerization of ε-caprolactone with hydroxy-terminated poly(N-vinylcaprolactam) (PNVCL-OH) as a macroinitiator. The structures of the polymers were confirmed by IR, ¹H NMR and GPC. The critical micelle concentrations of copolymer in aqueous solution measured by the fluorescence probe technique reduced with the increasing of the proportion of hydrophobic parts, so did the diameter and distribution of the micelles determined by dynamic light scattering. The shape observed by transmission electron microscopy (TEM) demonstrated that the micelles are spherical. On the other hand, the UV–vis measurement showed that polymers exhibit a reproducible temperature-responsive behavior with a lower critical solution temperature (LCST). The LCST of PNVCL-OH can be adjusted by controlling the molecular weights, and that of copolymers can be adjusted by controlling the compositions and the concentration. Variable temperature TEM measurements demonstrated that LCST transition was the result of transition of individual micelles to larger aggregates.     

Synthesis and drug-release properties of biodegradable hydrogels having β-cyclodextrin

A new β-cyclodextrin (β-CD) methacrylated monomer was synthesized from the reaction of β-CD, glycidyl methacrylate. Based on inclusion character of β-CD, a series of hydrogels were prepared by irradiating the mixtures of β-CD methacrylate monomer (β-CD-Met), poly(ethylene glycol) monoacrylate, poly(ethylene glycol)diacrylate, fumaric acid monoethyl ester-functionalized poly(lactic-co-glycolic) acid, 1-vinyl-2-pyrrolidone, N,N′-methylene bisacrylamide, and the photoinitiator. Gel percentages and equilibrium swelling ratios (%) of hydrogels were investigated. It was observed that equilibrium-swelling ratio increased with increasing β-CD-Met content in the hydrogel composition. SEM images demonstrated that β-CD-Met-based hydrogel have lots of voids on the fractured surface. In this study, ibuprofen (IBU) which is capable of forming inclusion complex with β-CD was chosen. For the hydrogel with maximum CD content, the IBU drug loading was found as 9 mg/g dry gel. It can be concluded that the inclusion complex-formation capability of β-CD moiety increases the drug release by improving the aqueous solubility of hydrophilic drugs.     

Synthesis and characterization of biodegradable poly(ε-caprolactone)/poly(γ-benzyl <Emphasis Type="SmallCaps">l</Emphasis>-glutamate) block copolymer

A biodegradable poly(ε-caprolactone)/poly(γ-benzyl l-glutamate) (PCL-b-PBLG) block copolymer was synthesized by ring-opening polymerization of N-carboxy-γ-benzyl l-glutamate anhydride (BLG-NCA) with amine-terminated poly(ε-caprolactone) (PCL-NH₂) as a macroinitiator. The PCL-NH₂ was prepared by deprotection of a PCL-CH₂CH₂NHBoc, which was obtained by ring-opening polymerization of ε-caprolactone (ε-CL) initiated by Boc-aminoethanol (HOCH₂CH₂NHBoc) using stannous octanoate as catalyst under microwave irradiation. The structures of the block copolymers were determined by IR, ¹H NMR, and GPC measurements. The results prove that BLG-NCA can be initiated by PCL-NH₂ to produce PCL-b-PBLG block copolymers.     

Core-shell structured nanoassemblies based on β-cyclodextrin containing block copolymer and poly(β-benzyl L-aspartate) via host-guest complexation

Double hydrophilic copolymers (PEG-b-PCDs) with one PEG block and another block containing β-cyclodextrin (β-CD) units were synthesized by macromolecular substitution reaction. Via a dialysis procedure, complex assemblies with a core-shell structure were prepared using PEG-b-PCDs in the presence of a hydrophobic homopolymer poly(β-benzyl l-aspartate) (PBLA). The hydrophobic PBLA resided preferably in the cores of assemblies, while the extending PEG chains acted as the outer shell. Host-guest interaction between β-CD and hydrophobic benzyl group was found to mediate the formation of the assemblies, where PEG-b-PCD and PBLA served as the host and guest macromolecules, respectively. The particle size of the assemblies could be modulated by the composition of the host PEG-b-PCD copolymer. The molecular weight of the guest polymer also had a significant effect on the size of the assemblies. The assemblies prepared from the host and guest polymer pair were stable during a long-term storage. These assemblies could also be successfully reconstituted after freeze-drying. The assemblies may therefore be used as novel nanocarriers for the delivery of hydrophobic drugs.     

Synthesis and self-assembly of comb-like amphiphilic Doxifluridine-poly(?-caprolactone)-graft-poly(γ-glutamic acid) copolymer

Advances in amphiphilic copolymers can potentially be exploited in drug or gene delivery. This study develops novel comb-like amphiphilic copolymers that comprise poly(γ-glutamic acid) (γ-PGA) as a hydrophilic backbone and Doxifluridine-poly-(?-caprolactone) (5′-deoxy-5-fluorouridine-poly(?-caprolactone), 5′DFUR-PCL) as a hydrophobic side chain. A novel 5′DFUR-PCL polymer was synthesized with antitumor agent Doxifluridine (5′DFUR) as the initiator via the ring-opening polymerization of ?-caprolactone (?-CL) using tin(II) 2-ethylhexanoate (Sn(Oct)₂) as the catalyst. The 5′DFUR-PCL polymer was then grafted on γ-PGA to yield a 5′DFUR-PCL-γ-PGA comb-like copolymer with the help of 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide (EDC). The characteristics of these copolymers were examined by ¹H NMR, FT-IR, GPC, contact angle measurement and thermal properties. Grafting 5′DFUR-PCL would significantly increase the contact angle and decrease the melting temperature (T_m) of the copolymers. The micelles self-assembled from these amphiphilic copolymers were formed in an aqueous phase and were examined via fluorescence approaches, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The average sizes of the micelles were in the range from 130 to 230 nm and their zeta potentials were negative and less than −16.7 mV. The critical micelle concentration (CMC) was from 1.49 mg/L to 4.63 mg/L at 25 °C. TEM images demonstrated that the micelles were spherical and clearly had a core-shell structure.     

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 50–130 nm 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.     

Structure and Performance of Poly(vinyl alcohol)/Poly(γ-benzyl L-glutamate) Blend Membranes

Poly(vinyl alcohol) (PVA)/poly(γ-benzyl L-glutamate) (PBLG) blend membranes with different PBLG wt contents were prepared by pervaporation. Structure and surface morphologies of PVA/PBLG blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PVA/PBLG blend membrane were studied by differential scanning calorimeter (DSC), tensile strength tests, and other physical methods. It was revealed that the introduction of PBLG homopolymer into PVA could exert an outstanding effect on the properties of PVA membrane.     

Synthesis of amphiphilic macrocyclic graft copolymer consisting of a poly(ethylene oxide) ring and multi-poly(?-caprolactone) lateral chains

A series of amphiphilic macrocyclic graft copolymers composed of a hydrophilic poly(ethylene oxide) as ring and hydrophobic poly(?-caprolactone) as lateral chains with different grafting lengths and densities of side chains were prepared by a combination of anionic ring-opening polymerization and coordination-insertion ring-opening polymerization. The anionic ring-opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using triethylene glycol and diphenylmethyl potassium (DPMK) as co-initiators, and a linear α,ω-dihydroxyl poly(ethylene oxide) with pendant protected hydroxymethyls (l-poly(EO-co-EEGE)) was obtained. The monomer reactivity ratios of these compounds are r_1(EO) = 1.20 ± 0.01 and r_2(EEGE) = 0.76 ± 0.02, respectively. Then the ring closure of l-poly(EO-co-EEGE) was achieved via an ether linkage by reaction with tosyl chloride (TsCl) in the presence of solid KOH. The crude cyclized product containing the linear chain-extended polymer was hydrolyzed in acidic conditions first and then purified by treating with α-CD. The pure cyclic copolymer of EO and glycidol (Gly) with multipendant hydroxymethyls [c-poly(EO-co-Gly)] as the macroinitiator was used further to initiate the ring-opening polymerization of ?-caprolactone (CL), and a series of amphiphilic macrocyclic graft copolymers c-PEO-g-PCL were obtained. The final products and intermediates were characterized by GPC, NMR and MALDI-TOF in detail.     

Synthesis and enzymatic degradation of poly(ε-caprolactone-co-ethylene carbonate-co-ethylene oxide) copolymer

Poly(ε-caprolactone-co-ethylene carbonate-co-ethylene oxide) (CL-co-EC-co-EO) copolymer was synthesized via ring-opening copolymerization of ε-caprolactone (CL) and 1,3-dioxolan-2-one with a metal-free phosphazene catalyst (t-BuP₄). The monomer conversion and molecular weight in CL-co-EC-co-EO copolymer were characterized by nuclear magnetic resonance and gel permeation chromatography, respectively. Moreover crystallization behavior of CL-co-EC-co-EO copolymer was investigated by differential scanning calorimeter and wide-angle X-ray diffraction. The enzymatic degradation of the copolymer has been investigated by quartz crystal microbalance with dissipation. Our studies demonstrate that as PCL content in the copolymer decreases, the degree of crystallinity and crystal size decrease, while the enzymatic degradation rate increases. The copolymer exhibits layer-by-layer degradation.     

pH-responsive amphiphilic H-shaped supramolecular copolymer via the inclusion complexation between β-cyclodextrin and adamantane

pH-responsive amphiphilic H-shaped copolymer was prepared by the supramolecular self-assembly between β-cyclodextrin-graft-poly(2-(N,N-diethylamino)ethyl methacrylate) (β-CD-(PDEAEMA)₂) and bi-adamantyl terminated poly(ε-caprolactone) (Ad-PCL-Ad). β-CD-(PDEAEMA)₂ was synthesized by click reaction of alkynyl-modified β-CD with azide PDEAEMA (PDEAEMA-N₃). Ad-PCL-Ad was synthesized by the DCC reaction of bi-hydroxyl terminated PCL (HO-PCL-OH) with adamantaneacetic acid. The supramolecular copolymer can self-assemble into micelles in water at room temperature. The micellization and pH-responsivity of the amphiphilic copolymer solution were investigated by transmittance, dynamic light scattering spectrophotometer, and transmission electron microscopy in water. Investigation shows that the micelles’ sizes can be adjusted through the alteration of the pH values of solutions and the supramolecular copolymer will have the potential applications in biomedical field.     

Synthesis and characterization of a novel amphiphilic poly (ethylene glycol)–poly (ε-caprolactone) graft copolymers

A series of amphiphilic graft copolymers PEO-g-PCL with different poly (ε-caprolactone) (PCL) molecular weight were successfully synthesized by a combination of anionic ring-opening polymerization (AROP) and coordination-insertion ring-opening polymerization. The linear PEO was produced by AROP of ethylene oxide (EO) and ethoxyethyl glycidyl ether initiated by 2-(2-methoxyethoxy) ethoxide potassium, and the hydroxyl groups on the backbone were deprotected after hydrolysis. The ring-opening polymerization of CL was initiated using the linear poly (ethylene oxide) (PEO) with hydroxyl group on repeated monomer as macroinitiator and Sn(Oct)₂ as catalyst, then amphiphilic graft copolymers PEO-g-PCL were obtained. By changing the ratio of monomer and macroinitiator, a series of PEO-g-PCL with well-defined structure, molecular weight control, and narrow molecular weight distribution were prepared. The expected intermediates and final products were confirmed by ¹H NMR and GPC analyzes. In addition, these amphiphilic graft copolymers could form spherical aggregates in aqueous solution by self-assemble, which were characterized by transmission electron microscopy, and the critical micelle concentration values of graft copolymers PEO-g-PCL were also examined in this article.     

Synthesis and hydrolysis of β-cyanoethyl ether of poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) was cyanoethylated by reaction with acrylonitrile in the presence of sodium hydroxide and quaternary ammonium halide. Quaternary ammonium halide, acting as a phase transfer catalyst, increases the degree of substitution (DS) of PVA. The DS also increased with increasing acrylonitrile concentration. Cyanoethylation of PVA up to 98% can be achieved under optimum conditions. The hydrolysis of β-cyanoethyl ether of PVA (CN–PVA) was studied. The rate of hydrolysis was affected by the sodium hydroxide concentration and the reaction temperature. The rheological properties of aqueous solution of hydrolysis product of CN–PVA were determined at different temperatures, and the flow activation energy was calculated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2771–2777, 1999     

Synthesis and characterization of a functionalized biodegradable copolymer: poly(l-lactide-co-RS-β-malic acid)

The ring-opening copolymerization of l-lactide (l-LA) and RS-β-benzyl malate (MA) was performed in the presence of stannous octoate. Copolymers were successfully synthesized using different feeding doses. ¹H NMR analysis revealed that the compositions of the copolymers with high MA contents were similar to the feeding doses. GPC measurements showed that the molecular weight of the copolymers decreased as the MA content increased. The hydrophilicity of these copolymers was remarkably improved after they were hydrogenolyzed over palladium on charcoal, which removed the pendant benzyl groups. These de-protected copolymers had higher glass transition temperatures (T_g) than both the corresponding protected copolymers and the PLLA homopolymer due to the formation of intermolecular hydrogen bonds between the pendant carboxyl groups. The morphology of the copolymers changed from crystalline to amorphous with increasing RS-β-malic acid content.     

Surface Morphology and Properties of Poly(γ-benzyl L-glutamate)/Poly(butyl acrylate-co-methyl Methacrylate) Blend Film

Poly(γ-benzyl L-glutamate)/poly(butyl acrylate-co-methyl methacrylate) (PBLG/Poly(BA-co-MMA)) blend films were prepared by casting the polymer blend solution in dichloroethane. Surface morphology of the polymer blend film was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Thermal and mechanical properties of the polymer blend film were studied using differential scanning calorimeter (DSC) and tensile tests. It was revealed that the introduction of Poly(BA-co-MMA) into PBLG could exert marked effects on the surface morphology and the properties of the PBLG film.     

Synthesis and characterization of (poly (N-vinyl formamide)—pregelled starch—graft copolymer

Bromate / cyclohexanone redox system was investigated as a novel initiator for graft copolymerization of N-vinyl formamide onto pregelled starch. A number of variables in the grafting reaction were investigated including N-vinyl formamide, cyclohexanone, bromate ion, sulphuric acid and pregelled starch concentrations, material to liquor ratio along with polymerization time and temperature. The graft copolymers were evaluated in terms of graft yield, graft reaction efficiency and homopolymer formation (%). The optimum conditions for grafting of N-vinyl formamide onto pregelled starch are: N-vinyl formamide 50% based on weight of substrate, cyclohexanone 15 mmol / l, bromate ion, 30 mmol / l, liquor ratio 10, pH 6, time 120 min., and temperature 40°C. On the other hand, characterizations of the resultant copolymers with respect to swelling capacity, solubility %, metal ion up-take and suitability as a sizing agent for cotton textiles were investigated. The results obtained reflect that, the resultant copolymer shows better results for the aforementioned properties in comparison with that obtained from native pregelled starch as a starting substrate.     

Synthesis and characterization of a novel graft copolymer with poly(n-octylallene-co-styrene) backbone and poly(?-caprolactone) side chain

A novel graft copolymer consisting of poly(n-octylallene-co-styrene) (PALST) as backbone and poly(?-caprolactone) (PCL) as side chains was synthesized with the combination of coordination copolymerization of n-octylallene and styrene and the ring-opening polymerization (ROP) of ?-caprolactone. Poly(n-octylallene-co-styrene) (PALST) backbone was prepared from the copolymerization of n-octylallene and styrene with high yield by using the coordination catalyst system composed of bis[N,N-(3,5-di-tert-butylsalicylidene)anilinato]titanium(IV) dichloride (Ti(Salen)₂Cl₂) and tri-isobutyl aluminum(Al(i-Bu)₃). The molar ratio of each segment in the copolymer, and the molecular weight of the copolymer as well as the microstructure of the copolymer could be adjusted by varying the feeding ratio of both styrene and n-octylallene. The hydroxyl functionalized copolymer PALST-OH was prepared by the reaction of mercaptoethanol with the pendant double bond of PALST in the presence of radical initiator azobisisbutyronitrile (AIBN). The target graft copolymer [poly(n-octylallene-co-styrene)-g-polycaprolactone] (PALST-g-PCL) was synthesized through a grafting-from strategy via the ring-opening polymerization using PALST-OH as macroinitiator and Sn(Oct)₂ as catalyst. Structures of resulting copolymer were characterized by means of gel permeation chromatography (GPC) with multi-angle laser light scattering (MALLS), ¹³C NMR, ¹H NMR, DSC, polarized optical microscope (POM) and contact angle measurements.     

Surface Morphology and Properties of Rigid Poly(γ-benzyl L-glutamate) Membrane Modified by Flexible Poly(Vinyl Chloride)

Rigid poly(γ-benzyl L-glutamate)/flexible poly(vinyl chloride) (PBLG/PVC) blend membranes were prepared by casting the polymer blend solution in dichloroethane. Structure and morphologies of the PBLG/PVC blend membranes were investigated by Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PBLG/PVC blend membranes were studied by differential scanning calorimetry (DSC), tensile tests, and other physical methods. It was found that the introduction of PVC could exert marked effects on the morphology and the properties of PBLG membrane.     

Morphology and Properties of Poly(γ-benzyl L-glutamate)-block-poly(ethylene glycol)/Poly(L-lactic acid) Blend Membrane

A series of poly(γ-benzyl L-glutamate)-block-poly(ethylene glycol) (PBLG-block-PEG)/poly(L-lactic acid) (PLLA) blend membranes were prepared by casting the polymer blend solution in chloroform. Surface morphologies of the PBLG-block-PEG/PLLA blend membranes were investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PBLG-block-PEG/PLLA blend membranes were studied by thermogravimetric analysis (TGA), tensile tests, and contact angle testing. It was found that the introduction of PLLA could exert outstanding effects on the morphology and the properties of polypeptide copolymer membrane.     

Preparation and sorption studies of microsphere copolymers containing β-cyclodextrin and poly(acrylic acid)

Microsphere polymeric materials containing β-cyclodextrin (β-CD) and poly(acrylic acid) (PAA) with tunable morphologies were prepared in order to improve their sorption characteristics in aqueous solution. The microsphere polymeric materials were prepared using a (water/oil) micro-emulsion-evaporation technique to condense β-cyclodextrin (β-CD) with PAA at various comonomer ratios and mixing speeds. The β-CD microsphere copolymers were characterized using FTIR, TGA, DSC, SEM, elemental (C and H) microanalyses, and solid state ¹³C-NMR spectroscopy. The sorption properties of the polymeric materials at 295 K in aqueous solution containing p-nitrophenol (PNP) were studied using a dye-based method with UV–Vis spectrophotometry at pH 4.6 and 10.3. The sorption isotherms of copolymer/PNP systems were evaluated with various isotherm models (e.g., Langmuir, BET, Freundlich, and Sips). The Sips isotherm showed the best overall agreement with the experimental results and the sorption parameters provided estimates of the sorbent surface area (12.0–331 m²/g) and the sorption capacity (Q_m = 0.359–2.20 mmol/g at pH = 4.6; Q_m = 0.070–0.191 mmol/g at pH = 10.3) for the microsphere copolymer/PNP systems in aqueous solution. The nitrogen adsorption properties of the microporous copolymers in the solid state were obtained at 77K with BET surface areas ranging from 0.275 to 4.47 m²/g. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012