Synthesis and characterization of polyrotaxanes comprising α-cyclodextrins and poly(ε-caprolactone) end-capped with poly(N-isopropylacrylamide)s

Biodegradable polyrotaxane (PR)-based triblock copolymers were synthesized via the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm) initiated with polypseudorotaxanes (PPRs) consisting of a distal 2-bromopropiomyl bromide end-capping poly(ε-caprolactone) (Br-PCL-Br) and a varying amount of α-cyclodextrins (α-CDs) in the presence of Cu(I)Br/PMDETA at 25 °C in aqueous solution. The copolymers were featured by relatively higher yields from 46.0% to 82.8% as compared with previous reports. Their structure was characterized in detail by using ¹H NMR, ¹³C CP/MAS NMR, GPC, WXRD, DSC and TGA analyses. When a feed molar ratio of NIPAAm to Br-PCL-Br was changed from 50 to 200, the degree of polymerization of PNIPAAm blocks attached to two ends of PPRs was in a range of 158–500. About one third of the added α-CDs were still entrapped on the central PCL chain after the ATRP process. Attaching PNIPAAm rendered the copolymers soluble in aqueous solution showing the thermo-responsibility as evidenced by turbidity measurements.     

Novel polyrotaxanes comprising γ-cyclodextrins and Pluronic F127 end-capped with poly(N-isopropylacrylamide) showing solvent-responsive crystal structures

Herein novel polyrotaxanes (PRs) comprising γ-CDs and Pluronic F127 end-capped using poly(N-isopropylacrylamide) blocks were prepared via the atom transfer radical polymerization in aqueous medium at room temperature. The structure was characterized in detail by ¹H NMR, 2D NOESY NMR, FTIR, GPC, WXRD and DSC analyses. Solvent treatments were conducted on the resulting PRs via incubation in water and DMF, respectively. Interestingly the treatments resulted in two crystal structures: the DMF-incubated PRs appeared to give a novel crystal structure, while the water treated samples yielded a typical channel-type crystal structure. The entrapped γ-CDs were found to be aggregated mainly around the central PPO segment in the DMF-incubated PRs while some of γ-CDs were randomly dispersed on the PEO segments in the water treated samples. The two crystal structures exhibited a strong solvent dependence and were convertible through solvent incubation. The solubility and flexibility were greatly changed with the crystal structure conversion. Hence this provides an opportunity to alter the physical properties of PRs without any chemical modification of entrapped CDs. The aggregated/dispersed state of γ-CDs along the Pluronic F127 chain as a result of response to solvent treatment renders the PRs great potential to be used as smart materials.     

Formation of antibiotic,biodegradable polymers by processing with Irgasan DP300R (triclosan) and its inclusion compound with β-cyclodextrin

The inclusion compound (IC) between the FDA-approved antibacterial Irgasan DP300 (Trichlosan), and β-cyclodextrin (CD) has been formed. When the Irgasan–β-CD–IC is embedded in biodegradeable/bioabsorbable films of poly(ϵ-caprolactone) (PCL) at low levels (a few wt %), they are rendered resistant to the growth of E. coli bacteria. When these same PCL films embedded with Irgasan–β-CD–IC are used as the adhesive for laminating cotton fabrics, we observe the resulting cotton laminates to also be resistant to the growth of E. coli bacteria. These results hold promise for the fabrication of bacteria-resistant polymer films and fibers, as well as antibacterial fabrics, by means of simple melt processing with Irgasan–β-CD–IC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 300–309, 2001     

Poly(ε-caprolactone) electrospun nanofibers containing curcumin nanocontainers: enhanced solubility,dissolution and physical stability of curcumin via formation of inclusion complex with cyclodextrins

Supramolecular nanocontainers of cyclodextrins (α- and β-CD)/curcumin (CUR) were prepared by inclusion complex (IC) forming between CDs and guest molecule at two conditions. Formation of the inclusion complex between CDs and CUR at various conditions in solid phase was characterized by various methods. Solubility and in vitro dissolution of obtaining CUR nanocapsules were investigated and results showed that encapsulation of CUR, improved CUR bioavailability with a controllable release. Electrospun nanofibers of poly-ε-caprolactone (PCL) containing CUR/CDs inclusion complex of various conditions have been fabricated using a conventional electrospinning process and indicated that these nanofibers are bead-free.     

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.     

Breathable Materials and Hybrid Nanocomposites with Antimicrobial Activity Based on Porous Poly(ε-Caprolactone) Obtained via Environmental Crazing

Structural modification of poly(ε-caprolactone) (PCL) allows the fabrication of new functional materials obtained via the PCL films/fibers stretching in ethanol by the crazing mechanism. Atomic force microscopy, X-ray scattering, and differential scanning calorimetry are employed to study the evolution of PCL structure. It is shown that ethanol plasticizes the polymer being deformed, and the stretching of PCL films/fibers occurs with formation of a fibrillar-porous structure in the interlamellar space. The obtained porous matrices have pore size below 50 nm and bulk porosities of 28% and 48% for fibers and films, respectively. Thermal stabilization of the PCL films’ porous structure made it possible to obtain breathable materials with a vapor permeability of 625–652 g m⁻² per day. The resulting porous PCL fibers and films can be used as matrices for the incorporation of useful additives and preparation of functional nanocomposites (NCs), biodegradable surgical suture, packaging, covering, and textile vapor-permeable materials. Hybrid NCs with antibacterial and fungicidal activities are obtained on the basis of the porous PCL matrices and functional components (5% silver, 1% brilliant green, 28% Betadine, etc.) incorporated into them.     

Synthesis, characterization and fluorescence adjustment of well-defined polymethacrylates with pendant π-conjugated benzothiazole via atom transfer radical polymerization (ATRP)

Two compounds containing the benzothiazole moiety, 4-(2-benzothiazole-2-yl-vinyl)-phenyl methacrylate (BVMA) and 2-bromo-2-methyl-propionic acid 4-(2-benzothiazole-2-yl-vinyl)-phenyl ester (BPBVE) were synthesized. Atom transfer radical polymerization (ATRP) of BVMA was conducted at 60 °C using BPBVE and CuBr/2,2′-bipyridine (BPY) as initiator and catalyst, respectively. Chain extension with 4-methacryloxy-hexyloxy-4′-nitrostilbene (MHNS) was conducted using PBVMA as the macroinitiator. The homopolymer PBVMA in DMF solution emitted blue fluorescence, and the copolymer PBVMA-b-PMHNS emitted orange fluorescence at about 610 nm due to the intramolecular energy transfer. ATRP of BVMA was also conducted using 2-bromo-2-methyl-propionic acid 4-nitrostilbene-hexyloxy ester (BPNHE) as an initiator. The obtained polymer was characterized via ¹H NMR and the fluorescence intensity was found to change with increasing number average molecular weight (M_n). The polymer with M_n = 15900 emitted white fluorescence in DMF solution.     

Main-group lead complexes with mixed 2,9-bis(4′-pyridyl) tetrathiafulvalene and 9-anthracenecarboxylate ligands

Although TTF coordination complexes with transition metals have been extensively studied, coordination chemistry of p-block metal ions with TTF ligands remains largely unexplored. In this study, two Pb(II) complexes of 2,6-bis(4′-pyridyl)tetrathiafulvalene (py-TTF-py) with co-coordinated 9-anthracenecarboxylate (AC), formulated as [Pb(AC)₂(py-TTF-py)₂] (1), {[Pb(AC)₂(py-TTF-py)_0.5]·CH₃CN}_n (2), and a transition metal Cd(II) compound [Cd(AC)₂(py-TTF-py)₂]_n (3) for comparison are characterized by single-crystal X-ray diffraction. Compound 1 is a monomer and 3 is a 1-D compound. Compound 2 is a 2-D coordination polymer with planar mesh-like structure. They are metal linked electron donor and fluorescent acceptor system. Traced by the intensity of fluorescence quenching of AC ligand, it was found that Pb(II) ion is a good intermediary for ligand-to-ligand charge-transfer in this system.     

Suprarmolecular hydrogels driven by the dual host–guest interactions between α-cyclodextrin and ferrocene-modified poly(ethylene glycol) with low-molecular-weight

In general, α-cyclodextrin (α-CD) and low-molecular weight poly(ethylene glycol) (low-MW PEG) (M_w = 400–10,000) cannot construct supramolecular hydrogels but easily form crystalline precipitates. In this study, low-MW PEG (M_n = 2000, PEG-2000) was functionalized by ferrocene as mono-end-group. The obtained ferrocene-modified PEG-2000 (FcPEG-2000) further self-assembled into supramolecular hydrogel with α-CD even at low concentration (C_FcPEG-2000 = 17 mg/ml), driven by dual host–guest interaction between α-CD and FcPEG-2000. Interestingly, the hydrogel was still observed even when hydrophobic Fc group was oxidized to hydrophilic ferrocenium (Fc⁺) or included into the cavity of β-CD. In the former case, the existence of Fc⁺ end groups is considered to decrease the probability of PEG de-penetration from α-CD cavity, so that α-CDs have more location and opportunities to aggregate into more channel-type crystalline domains as physical cross-linking points. While in the later case, the synergistic effect of host–guest interaction between β-CD and ferrocenyl groups and host–guest interaction between α-CD and PEG chains are considered to be the main reason. The resultant FcPEG-2000 based hydrogels showed the property of shear-thinning.     

Iridium(III) complexes based on 5-nitro-2-(2′,4′-difluorophenyl)pyridyl: Syntheses,structures and photoluminescence properties

A series of cyclometalated Ir(III) complexes [Ir(dFNppy)₂(PPh₃)L] (PPh₃ = triphenylphosphine, L = Cl⁻, 1; NCS⁻, 2; NCO⁻, 3; N₃⁻, 4) in which 5-nitro-2-(2′,4′-difluorophenyl)pyridyl (dFNppy) is used as the main ligand are synthesized and characterized. The crystal structures of 3 and 4 are determined by X-ray diffraction analyses. Photoluminescence spectra of 1–4 in CH₂Cl₂ solutions at room temperature show the maximum emission wavelengths (λ_max) in the range from 586 to 627 nm, corresponding to red-orange luminescence. HOMO–LUMO energy levels of 1–4 are estimated by cyclic voltammetry measurements. Compared with corresponding 2-phenylpyridyl (ppy)-containing Ir(III) complexes having same ancillary ligands, 1–4 have obviously smaller HOMO–LUMO energy gaps (E_g). Simultaneously, 1–4 show relatively bigger E_g compared with 2-phenyl-5-nitropyridyl (5-NO₂-ppy)-containing Ir(III) complexes possessing same ancillary ligands. Methods of E_g adjustment are also discussed.     

Two novel 3D porous Copper(II) and Zinc(II) frameworks with 1,3-di-(1,2,4- triazole-4-yl)benzene: 4-connected dmp network versus 6-connnected α-Po network based on trinuclear Zinc(II) clusters

Used versatile multidentate benzene-based bis-triazole ligand 1,3-di-(1,2,4-triazole-4-yl)benzene (L), two novel 3D porous Copper(II) and Zinc(II) frameworks, namely {[Cu(μ₂-L)₂(SiF₆)(H₂O)]·0.5H₂O}_n (1) and {[Zn₃(μ₃-L)₆](NO₃)₆}_n (2), have been isolated under the hydrothermal conditions. The structural analysis reveals that 1 presents a 3D microporous Copper(II) framework with the novel 4-connected 6³8³ dmp topology containing infinite right- and left-handed Cu(μ₂-L)₂ helical chains. While 2 presents a 3D cluster-based nano-porous cationic host framework with 6-connected α-Po-related (4¹²6³) topology, in which trinuclear Zinc(II) clusters can be defined as basic nodes. The varied temperature magnetic susceptibility of 1 (from 300 to 2 K) and solid state luminescent property of 2 also have been investigated.     

Structure and Thermal Degradation Properties of Nanocomposites of Alanine Amino Acid-based Poly(amide–imide) Reinforced with Carboxymethyl-β-cyclodextrin Intercalated in a Layered Double Hydroxide

MgAl-layered double hydroxide was intercalated with carboxymethyl-β-cyclodextrin under ultrasonic conditions. Then, different percentages of carboxymethyl-β-cyclodextrin–functionalized layered double hydroxide (carboxymethyl-β-cyclodextrin-layered double hydroxide) was incorporated into the alanine amino acid-based poly(amide–imide) matrix via ultrasonic irradiations to obtain poly(amide–imide)/carboxymethyl-β-cyclodextrin-layered double hydroxide nanocomposites. The surface morphology and thermal degradation behavior of the poly(amide–imide)/carboxymethyl-β-cyclodextrin-layered double hydroxide nanocomposites have been examined by different techniques. The relatively good dispersion of carboxymethyl-β-cyclodextrin-layered double hydroxide into the poly(amide–imide) matrix was detected by transmission electron microscopy. Transmission electron microscopy images represented that the layered double hydroxide platelets were oriented separately and were not detected by X-ray diffraction, which means, the layered double hydroxide layers are exfoliated in the polymer.     

Spectral, Thermal and Structural Studies of Poly[μ-acetato(4-aminobenzoato)lead(II) monohydrate]: A Polymeric Hydrated Lead(II) Complex with Acetate Bridges

Single crystals of a lead(II) complex of 4-aminobenzoic acid, [Pb(Paba)(CH₃COO)]·H₂O (PabaH = 4-aminobenzoic acid) were successfully grown by gel diffusion technique using sodium metasilicate. The grown crystals were characterized by elemental analysis, fourier transform infrared (FT-IR) and UV–Vis spectroscopic techniques. The crystalline nature of the grown complex was confirmed by the powder X-ray diffraction (XRD) studies. FT-IR spectral studies were carried out to identify the functional groups. Thermal properties of the compound were studied using thermogravimetric analysis. The structure of the complex was elucidated by single crystal XRD studies. The title compound crystallizes in the centrosymmetric monoclinic space group P2₁/c and is having a polymeric structure. The polymeric array is constructed by the oxygen atom of acetate group and nitrogen atom of the aminobenzoate group.     

Inclusion complexes of atorvastatin calcium (ATV-Ca) and rosuvastatin calcium (ROV-Ca) drugs with α-CD, β-CD, γ-CD,HP-β-CD,M-β-CD,and maltodextrin along with their characterizations through experimental and computational methods

The aim of this research is a comparison of the efficiency of six commercially available cyclodextrins (CDs) to improve the solubility and oral bioavailability of atorvastatin calcium (ATV-Ca) and rosuvastatin calcium (ROV-Ca) drugs in aqueous media. Inclusion complexes of both drugs with non-toxic α-CD, β-CD, γ-CD, HP-β-CD, M-β-CD, and maltodextrin were prepared in a 1:1 stoichiometry via the kneading method. To reach the best CD, various experimental and computational analyses were performed including phase solubility, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), hydrogen-1 nuclear magnetic resonance (¹HNMR), carbon-13 nuclear magnetic resonance (¹³CNMR), and molecular docking calculations. The M-β-CD turned out to be the best substrate for the micro-encapsulation of both drugs. Also, ATV showed a higher tendency than ROV to form inclusion complexes with CDs. Molecular docking studies showed that HP–β–CD and M-β-CD are the most suitable substrates for the formation of inclusion complexes, respectively. Our research showed that the β-CD is not necessarily the most efficient substrate for increasing solubility based on previous reports in the literature; meanwhile, the other employed substrates in this study can show acceptable performances in this regard. According to our results, M-β-CD is the best substrate for the micro-encapsulation of both drugs, which increases their solubility in water.     

Six- and five-coordinated complexes of Co(II) with 2-(2′-pyridyl)quinoxaline. Crystal structures of the complexes [CoLCl2(DMF)] and [CoL2(H2O)2](ClO4)2·H2O·2CH3OH

Reaction of Co(II) perchlorate hexahydrate and anhydrous Co(II) chloride with the ligand 2-(2′-pyridyl)quinoxaline (L) leads to the formation of the novel five- and six-coordinated complexes CoLCl₂(DMF) (1) and [CoL₂(H₂O)₂](ClO₄)₂·H₂O·2CH₃OH (2), correspondingly. The crystal structures of the above complexes show a trigonal bipyramidal geometry around the metal atom for complex 1 and a distorted octahedral geometry for complex 2.     

Nanocomposite particles with core–shell morphology III: preparation and characterization of nano Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–poly(styrene–methyl methacrylate) particles via miniemulsion polymerization

Encapsulation of inorganic nanoparticles (as a core) by polymers (as a shell) is one of the interesting research subjects that lead to the synthesis of nanocomposite. These materials include properties of not only the organic polymer (e.g. optical properties, toughness, processability, flexibility, etc.) but also the inorganic nanoparticles (e.g. mechanical strength, thermal stability, etc.). Some of the applied preparative methods are dry-spray, dispersion, suspension, emulsion and miniemulsion polymerization techniques. Here, miniemulsion polymerization technique was used in order to obtain white-color nanocomposite latex particles containing nano-alumina (40–47 nm) encapsulated by copoly [styrene (St)–methyl methacrylate (MMA)] under high-shear ultrasonic irradiation. At first, bare nano-alumina was encapsulated with the copolymer to obtain latex particles. In another attempt and in order to investigate the effect of compatiblizing system, alumina nanoparticles were coated with oleic acid in order to form modified alumina core. Then miniemulsion polymerization was performed in the minidroplets including modified alumina, St and MMA for obtaining core/shell nanocomposite particles. The progress of encapsulation polymerization was followed by different instrumental techniques such as FT-IR spectra, thermal gravimetric analysis, dynamic light scattering, induced-coupled plasma, TEM and SEM.     

The 4th International Exhibition on Refractories, Industrial Ceramics and Furnaces(RCF Expo''''2003)Beijing, China, April 15-17, 2003In conjunction with China Refractories Seminar'''' 2003-Technology and Markets

Organizers and Sponsors: China Association of Refractories Industry The Chinese Society for Metals The Chinese Ceramic Society