Organic–inorganic hybrid brushes consisting of macrocyclic oligomeric silsesquioxane and poly(ε‐caprolactone): Synthesis,characterization, and supramolecular inclusion complexation with α‐cyclodextrin

Organic–inorganic hybrid brushes comprised of macrocyclic oligomeric silsesquioxane (MOSS) and poly(ε‐caprolactone) (PCL) were synthesized via the ring‐opening polymerization of ε‐caprolactone (CL) with cis‐hexa[(phenyl) (2‐hydroxyethylthioethyldimethylsiloxy)]cyclohexasiloxane as the initiator. The MOSS macromer bearing hydroxyl groups was synthesized via the thiol‐ene radical addition reaction between cis‐hexa[(phenyl)(vinyldimethylsiloxy)]cyclohexasiloxane and β‐mercaptoethanol. The organic–inorganic PCL cyclic brushes were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). These MOSS–PCL brushes were then used to prepare the supramolecular inclusion complexes with α‐cyclodextrin (α‐CD). The X‐ray diffraction (XRD) indicates that the organic–inorganic inclusion complexes (ICs) have a channel‐type crystalline structure. It is noted that the molar ratios of CL unit to α‐CD for the organic–inorganic ICs are quite dependent on the lengths of the PCL chains bonded to the silsesquioxane macrocycle. While the PCL chains were short, the efficiency of inclusion complexation was significantly decreased. The decreased efficiency could be attributed to the repulsion of the adjacent PCL chains bonded to the silsesquioxane macrocycle and the restriction of the bulky silsesquioxane macrocycle on the motion of PCL chains; this effect is pronounced with decreasing the length of the PCL chains. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Melting and crystallization behavior of polyhedral oligomeric silsesquioxane‐capped poly(ε‐caprolactone)

In this study, we investigated the melting and crystallization behavior of polyhedral oligomeric silsesquioxane (POSS)‐capped poly(ε‐caprolactone) PCL with various lengths of PCL chains by means of X‐ray diffraction and differential scanning calorimetry. This organic–inorganic macromolecule possesses a tadpole‐like structure in which the bulky POSS cage is the “head” whereas PCL chain the “tail”. The novel organic–inorganic association result in the significant alterations in the melting and crystallization behavior of PCL. The POSS‐terminated PCL displayed the enhanced equilibrium melting points compared to the control PCL. Both the overall crystallization rate and the spherulitic growth rate of the POSS‐terminated PCLs increased with increasing the concentration of POSS (or with decreasing length of PCL chain in the hybrids). The analysis of Avrami equation shows that the crystallization of the POSS‐terminated PCL preferentially followed the mechanism of spherulitic growth with instantaneous nuclei. It is found that the folding free energy of surface for the POSS‐terminated PCLs decreased with increasing the concentration of POSS. It is found that the folding free energy of surface for the POSS‐terminated PCLs decreased with increasing the concentration of POSS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2201–2214, 2007     

Supramolecular inclusion complexes of a star polymer containing cholesterol end‐capped poly(ε‐caprolactone) arms with β‐cyclodextrin

A novel hexa‐armed and star‐shaped polymer containing cholesterol end‐capped poly(ε‐caprolactone) arms emanating from a phosphazene core (N₃P₃‐(PCL‐Chol)₆) was synthesized by a combination of ring‐opening polymerization and “click” chemistry techniques. For this purpose, the terminal ? OH groups of the synthesized precursor (N₃P₃‐(PCL‐OH)₆) were converted into –Chol through a series of reaction. Both N₃P₃‐(PCL‐OH)₆ and N₃P₃‐(PCL‐Chol)₆ were then employed in the preparation of supramolecular inclusion complexes (ICs) with β‐cyclodextrin (β‐CD). The latter formed ICs with β‐CD in higher yield. The host–guest stoichiometry (ε‐CL:β‐CD, mol:mol) in the ICs of N₃P₃‐(PCL‐Chol)₆ was found to be 1.2. The formation of supramolecular ICs of N₃P₃‐(PCL‐Chol)₆ with β‐CD was confirmed by using Fourier transform infrared (FTIR) and ¹H nuclear magnetic resonance (NMR) spectroscopic methods, wide‐angle X‐ray diffraction (WAXD), and thermal analysis techniques. WAXD data showed that the obtained ICs with N₃P₃‐(PCL‐Chol)₆ had a channel‐type crystalline structure, indicating the suppression of the original crystallization of N₃P₃‐(PCL‐Chol)₆ in β‐CD cavities. Moreover, the thermal stabilities of ICs were found to be higher than those of the free star polymer and β‐CD. Furthermore, the surface properties of N₃P₃‐(PCL‐Chol)₆ and its ICs with β‐CD were investigated by static contact angle measurements. The obtained results proved that the wettability of N₃P₃‐(PCL‐Chol)₆ successfully increased with the formation of its ICs with β‐CD. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3406–3420     

Supramolecular inclusion complexes of star‐shaped poly(ε‐caprolactone) with α‐cyclodextrin

Both star‐shaped poly(ε‐caprolactone) (PCL) having 4 arms (4sPCL) and 6 arms (6sPCL) and linear PCL having 1 arm (LPCL) and 2 arms (2LPCL) were synthesized and then investigated for inclusion complexation with α‐cyclodextrin (α‐CD). The supramolecular inclusion complexes (ICs) were in detail characterized by ¹H NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X‐ray diffraction, solid‐state carbon nuclear magnetic resonance spectroscopy using cross‐polarization and magic‐angle spinning, and Fourier transform infrared, respectively. The stoichiometry (CL:CD, mol:mol) of all ICs increased with the increasing branch arm of PCL polymers, and it was in the order of α‐CD‐6sPCL1 ICs > α‐CD‐4sPCL ICs > α‐CD‐2LPCL ICs > α‐CD‐LPCL ICs. All analyses indicated that the branch arms of star‐shaped PCL polymers were included into the hydrophobic α‐CD cavities and their original crystalline properties were completely suppressed. Moreover, the ICs of star‐shaped PCL with α‐CD had a channel‐type crystalline structure similar to that formed between the linear PCL and α‐CD. Furthermore, the thermal stability of the free PCL polymers probably controlled that of the guest polymers included in the ICs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4721–4730, 2005     

Poly(ethylene imine)‐graft‐poly(ethylene oxide) brush‐like copolymers: Preparation,thermal properties,and selective supramolecular inclusion complexation with α‐cyclodextrin

Poly(ethylene imine)‐graft‐poly(ethylene oxide) (PEI‐g‐PEO) copolymers were synthesized via Michael addition reaction between acryl‐terminated poly(ethylene oxide) methyl ether (PEO) and poly(ethylene imine) (PEI). The brush‐like copolymers were characterized by means of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. It is found that the crystallinity of the PEO side chains in the copolymers remained unaffected by the PEI backbone whereas the crystal structure of PEO side chains was altered to some extent by the PEI backbone. The crystallization behavior of PEO blocks in the copolymers suggests that the bush‐shaped copolymers are microphase‐separated in the molten state. The PEO side chains of the copolymers were selectively complexed with α‐cyclodextrin (α‐CD) to afford hydrophobic side chains (i.e., PEO/α‐CD inclusion complexes). The X‐ray diffraction (XRD) shows that the inclusion complexes (ICs) of the PEO side chains displayed a channel‐type crystalline structure. It is identified that the stoichiometry of the inclusion complexation of the PEI‐g‐PEO with α‐CD is close to that of the control PEO with α‐CD. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2296–2306, 2008     

Organic–inorganic hybrid hydrogels involving poly(N‐isopropylacrylamide) and polyhedral oligomeric silsesquioxane: Preparation and rapid thermoresponsive properties

3‐Acryloxypropylhepta(3,3,3‐trifluoropropyl) polyhedral oligomeric silsesquioxane (POSS) was synthesized and used as a modifier to improve the thermal response rates of poly(N‐isopropylacrylamide) (PNIPAM) hydrogel. The radical copolymerization among N‐isopropylacrylamide (NIPAM), the POSS macromer and N,N′‐methylenebisacrylamide was performed to prepare the POSS‐containing PNIPAM cross‐linked networks. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) showed that the POSS‐containing PNIPAM networks displayed the enhanced glass transition temperatures (T_g's) and improved thermal stability when compared with plain PNIPAM network. The POSS‐containing PNIPAM hydrogels exhibited temperature‐responsive behavior as the plain PNIPAM hydrogels. It is noted that with the moderate contents of POSS, the POSS‐containing PNIPAM hydrogels displayed much faster response rates in terms of swelling, deswelling, and re‐swelling experiments than plain PNIPAM hydrogel. The improved thermoresponsive properties of hydrogels have been interpreted on the basis of the formation of the specific microphase‐separated morphology in the hydrogels, that is, the POSS structural units in the hybrid hydrogels were self‐assembled into the highly hydrophobic nanodomains, which behave as the microporogens and promote the contact of PNIPAM chains and water. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 504–516, 2009     

Preparation of novel poly(ethylene oxide‐co‐glycidol)‐graft‐poly(ε‐caprolactone) copolymers and inclusion complexation of the grafted chains with α‐cyclodextrin

A well‐defined comblike copolymer of poly(ethylene oxide‐co‐glycidol) [(poly(EO‐co‐Gly)] as the main chain and poly(ε‐caprolactone) (PCL) as the side chain was successfully prepared by the combination of anionic polymerization and ring‐opening polymerization. The glycidol was protected by ethyl vinyl ether to form 2,3‐epoxypropyl‐1‐ethoxyethyl ether (EPEE) first, and then ethylene oxide was copolymerized with EPEE by an anionic mechanism. The EPEE segments of the copolymer were deprotected by formic acid, and the glycidol segments of the copolymers were recovered after saponification. Poly(EO‐co‐Gly) with multihydroxyls was used further to initiate the ring‐opening polymerization of ε‐caprolactone in the presence of stannous octoate. When the grafted copolymer was mixed with α‐cyclodextrin, crystalline inclusion complexes (ICs) were formed, and the intermediate and final products, poly(ethylene oxide‐co‐glycidol)‐graft‐poly(ε‐caprolactone) and ICs, were characterized with gel permeation chromatography, NMR, differential scanning calorimetry, X‐ray diffraction, and thermogravimetric analysis in detail. The obtained ICs had a channel‐type crystalline structure, and the ratio of ε‐caprolactone units to α‐cyclodextrin for the ICs was higher than 1:1. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3684–3691, 2006     

Synthesis of four‐armed poly(ε‐caprolactone)‐block‐poly(ethylene oxide) by diethylzinc catalyst

Biodegradable, amphiphilic, four‐armed poly(?‐caprolactone)‐block‐poly(ethylene oxide) (PCL‐b‐PEO) copolymers were synthesized by ring‐opening polymerization of ethylene oxide in the presence of four‐armed poly(?‐caprolactone) (PCL) with terminal OH groups with diethylzinc (ZnEt₂) as a catalyst. The chemical structure of PCL‐b‐PEO copolymer was confirmed by ¹H NMR and ¹³C NMR. The hydroxyl end groups of the four‐armed PCL were successfully substituted by PEO blocks in the copolymer. The monomodal profile of molecular weight distribution by gel permeation chromatography provided further evidence for the four‐armed architecture of the copolymer. Physicochemical properties of the four‐armed block copolymers differed from their starting four‐armed PCL precursor. The melting points were between those of PCL precursor and linear poly(ethylene glycol). The length of the outer PEO blocks exhibited an obvious effect on the crystallizability of the block copolymer. The degree of swelling of the four‐armed block copolymer increased with PEO length and PEO content. The micelle formation of the four‐armed block copolymer was examined by a fluorescent probe technique, and the existence of the critical micelle concentration (cmc) confirmed the amphiphilic nature of the resulting copolymer. The cmc value increased with increasing PEO length. The absolute cmc values were higher than those for linear amphiphilic block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 950–959, 2004     

Inorganic–organic nanocomposites of polybenzoxazine with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane

Octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OpePOSS) was used to prepare the polybenzoxazine (PBA‐a) nanocomposites containing polyhedral oligomeric silsesquioxane (POSS). The crosslinking reactions involved with the formation of the organic–inorganic networks can be divided into the two types: (1) the ring‐opening polymerization of benzoxazine and (2) the subsequent reaction between the in situ formed phenolic hydroxyls of PBA‐a and the epoxide groups of OpePOSS. The morphology of the nanocomposites was investigated by means of scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Differential scanning calorimetry and dynamic mechanical analysis showed that the nanocomposites displayed higher glass‐transition temperatures than the control PBA‐a. In the glassy state, the nanocomposites containing less than 30 wt % POSS displayed an enhanced storage modulus, whereas the storage moduli of the nanocomposites containing more than 30 wt % POSS were lower than that of the control PBA‐a. The dynamic mechanical analysis results showed that all the nanocomposites exhibited enhanced storage moduli in the rubbery states, which was ascribed to the two major factors, that is, the nanoreinforcement effect of POSS cages and the additional crosslinking degree resulting from the intercomponent reactions between PBA‐a and OpePOSS. Thermogravimetric analysis indicated that the nanocomposites displayed improved thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1168–1181, 2006     

POSS end‐linked peptide‐functionalized poly(ɛ‐caprolactone)s and their inclusion complexes with α‐cyclodextrin

In this report, we have synthesized organic/inorganic hybrid peptide–poly(?‐caprolactone) (PCL) conjugates via ring opening polymerization (ROP) of ?‐caprolactone (CL) in the presence of two sequence defined peptide initiators, namely POSS‐Leu‐Aib‐Leu‐NH₂ (POSS: polyhedral oligomeric silsesquioxane; Leu: Leucine; Aib: α‐aminoisobutyric acid) and OMe‐Leu‐Aib‐Leu‐NH₂. Covalent attachment of peptide segments with the PCLs were examined by ¹H and ²⁹Si NMR spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) and FTIR spectroscopy. Supramolecular inclusion complexations of synthesized peptide‐PCL conjugates with α‐cyclodextrin (α‐CyD) were studied to understand the effect of POSS/OMe‐peptide moieties at the PCL chain ends. Inclusion complexation of peptide‐PCL conjugates with α‐CyD produced linear polypseudorotaxane, confirmed by ¹H NMR, FTIR, powder X‐ray diffraction (PXRD), polarized optical microscopy (POM) and differential scanning calorimetry (DSC). Extent of α‐CyD threading onto the hybrid peptide‐PCL conjugated polymers is less than that of α‐CyD threaded onto the linear PCL. Thus, PCL chains were not fully covered by the host α‐CyD molecules due to the bulky POSS/OMe‐peptide moieties connected with the one edge of the PCL chains. PXRD experiment reveals channel like structures by the synthesized inclusion complexes (ICs). Spherulitic morphologies of POSS/OMe‐peptide‐PCL conjugates were fully destroyed after inclusion complexation with α‐CyD and tiny nanoobjects were produced. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3643–3651.     

Novel Amphiphilic Degradable Poly(ε‐caprolactone)‐graft‐poly(4‐vinyl pyridine), Poly(ε‐caprolactone)‐graft‐poly(dimethylaminoethyl methacrylate) and Water‐Soluble Derivatives

New amphiphilic graft copolymers that have a poly(ε‐caprolactone) (PCL) biodegradable hydrophobic backbone and poly(4‐vinylpyridine) (P4VP) or poly(2‐(N,N‐dimethylamino)ethyl methacrylate) (PDMAEMA) hydrophilic side chains have been prepared by anionic polymerization of the corresponding 4VP and DMAEMA monomers using a PCL‐based macropolycarbanion as initiator. The water solubility of these amphiphilic copolymers is improved by quaternization, which leads to fully water‐soluble cationic copolymers that give micellar aggregates in deionized water with diameters ranging from 65 to 125 nm. In addition, to improve the hydrophilicity of PCL‐g‐P4VP, grafting of poly(ethylene glycol) (PEG) segments has been carried out to give a water‐soluble double grafted PCL‐g‐(P4VP;PEG) terpolymer.

     

Grafting of poly(ε‐caprolactone) onto maghemite nanoparticles

We report the coating of maghemite (γ‐Fe₂O₃) nanoparticles with poly(ε‐caprolactone) (PCL) through a covalent grafting to technique. ω‐Hydroxy‐PCL was first synthesized by the ring‐opening polymerization of ε‐caprolactone with aluminum isopropoxide and benzyl alcohol as a catalytic system. The hydroxy end groups of PCL were then derivatized with 3‐isocyanatopropyltriethoxysilane in the presence of tetraoctyltin. The triethoxysilane‐functionalized PCL macromolecules were finally allowed to react on the surface of maghemite nanoparticles. The composite nanoparticles were characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Effects of the polymer molar mass and concentration on the amount of polymer grafted to the surface were investigated. Typical grafting densities up to 3 μmol of polymer chains per m² of maghemite surface were obtained with this grafting to technique. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6011–6020, 2004     

Synthesis,characterization, and degradation of poly(ethylene‐b‐ε‐caprolactone) diblock copolymer

Poly(ethylene‐b‐ε‐caprolactone) (PE‐b‐PCL) diblock copolymers were synthesized by ring‐opening polymerization (ROP) of ε‐caprolactone (CL) with α‐hydroxyl‐ω‐methyl polyethylene (PE‐OH) as a macroinitiator and ammonium decamolybdate (NH₄)₈[Mo₁₀O₃₄] as a catalyst. Polymerization was conducted in bulk (130–150°C) with high yield (87–97%). Block copolymers with different compositions were obtained and characterized by ¹H and ¹³C NMR, MALDI‐TOF, SAXS, and DSC. End‐group analysis by NMR and MALDI‐TOF indicates the formation of α‐hydroxyl‐ω‐methyl PE‐b‐PCL. The PE‐b‐PCL degradation was studied using thermogravimetric analysis (TGA) and alkaline hydrolysis. The PCL block was hydrolyzed by NaOH (4M), without any effect on the PE segment. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of poly(β‐hydroxybutyrate) and poly(ϵ‐caprolactone) copolyester by transesterification

To synthesize the copolyester of poly(β‐hydroxybutyrate) (PHB) and poly(?‐caprolactone) (PCL), the transesterification of PHB and PCL was carried out in the liquid phase with stannous octoate as the catalyzer. The effects of reaction conditions on the transesterification, including catalyzer concentration, reaction temperature, and reaction time, were investigated. The results showed that both rising reaction temperature and increasing reaction time were advantageous to the transesterification. The sequence distribution, thermal behavior, and thermal stability of the copolyesters were investigated by ¹³C NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, optical microscopy, and thermogravimetric analysis. The transesterification of PHB and PCL was confirmed to produce the block copolymers. With an increasing PCL content in the copolyesters, the thermal behavior of the copolyesters changed evidently. However, the introduction of PCL segments into PHB chains did not affect its crystalline structure. Moreover, thermal stability of the copolyesters was little improved in air as compared with that of pure PHB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1893–1903, 2002     

Preparation of Porous Poly(ε‐caprolactone) Structures

Porous poly(ε‐caprolactone) structures have been prepared by leaching of compression moulded salt‐containing polymer precipitates. Coagulation takes place when a PCL solution containing dispersed water‐soluble salt particles is precipitated into an excess of non‐solvent. Porous scaffolds are obtained after leaching of the compression moulded polymer‐salt precipitate. This process yields scaffolds with a very homogeneous pore morphology and independent control of pore size and porosity.     

Supramolecular polyseudorotaxanes formation between star‐block copolymer and α‐cyclodextrin: From outer block to diblock inclusion complexation

A series of star‐block poly(L ‐lactide)‐b‐poly(ethylene oxide) (SPLLA‐b‐PEO) copolymers were synthesized by ring‐opening polymerization (ROP) and DCC chemistry. The inclusion complexes of SPLLA‐b‐PEO copolymers and α‐cyclodextrin (α‐CD) were prepared with two different methods. FTIR, ¹H NMR, WAXD, DSC, and TGA indicate that α‐CD only can be threaded onto PEO blocks in inclusion complexes of α‐CD‐SPLLA‐b‐PEO1.1K‐a, α‐CD‐SPLLA‐b‐PEO2K‐a, and α‐CD‐SPLLA‐b‐PEO5K‐a formed without heating and ultrasonication, and can be threaded onto both PLLA and PEO blocks in inclusion complexes of α‐CD‐SPLLA‐b‐PEO1.1K‐b, α‐CD‐SPLLA‐b‐PEO2K‐b, and α‐CD‐SPLLA‐b‐PEO5K‐b formed with heating and ultrasonication. Namely, α‐CDs can be threaded onto PEO blocks and the flanking bulky PLLA blocks of star‐block copolymers to form stable polyseudorotaxanes with heating method and ultrasonication to conquer the activation energy barrier of the inclusion complexation between bulky PLLA and α‐CD and the effect of the steric hindrance of star‐block copolymers. With the alteration of preparing methods, the inclusion complexes of α‐CD with the outer PEO block or PEO and PLLA blocks were obtained successfully. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2754–2762, 2009     

Synthesis of well‐defined star‐shaped poly(ε‐caprolactone)/poly(ethylbene glycol) amphiphilic conetworks by combination of ring opening polymerization and “click” chemistry

Well‐defined star‐shaped hydrophobic poly(ε‐caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) amphiphilic conetworks (APCNs) have been synthesized via the combination of ring opening polymerization (ROP) and click chemistry. Alkyne‐terminated six arm star‐shaped PCL (6‐s‐PCLx‐C?CH) and azido‐terminated PEG (N₃‐PEG‐N₃) are characterized by ¹H NMR and FT‐IR. The swelling degree of the APCNs is determined both in water and organic solvent. This unique property of the conetworks is dependent on the nanophase separation of hydrophilic and hydrophobic phases. The morphology and thermal behaviors of the APCNs are investigated by SEM and DSC respectively. The biocompatibility is determined by water soluble tetrazolium salt reagents (WST‐1) assay, which shows the new polymer networks had good biocompatibility. Through in vitro release of paclitaxel (PTX) and doxorubicin (DOX), the APCNs is confirmed to be promising drug depot materials for sustained hydrophobic and hydrophilic drugs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 407–417     

The spectrophotometric study of a fluorescence‐enhanced inclusion complex threaded with β‐cyclodextrin: Synthesis and characterization

A novel achiral monomer end‐capped with a phenyl‐[1,3,4]oxadiazolyl group and threaded through β‐cyclodextrin was synthesized to investigate the host‐guest interactions in the inclusion complex. ¹H NMR studies revealed that one or two cyclodextrin molecules were threaded onto the synthesized achiral monomer, leading to the formation of a fibrous construction of self‐assembled inclusion complexes. The formation of a self‐assembled inclusion complex was identified using SEM and TEM. The highly ordered alignment of self‐assembled supramolecules was confirmed using polarized optical microscopy. We demonstrate an easy process for the fabrication of nano‐structured self‐assembled inclusion complexes in pyridine/ethanol (1 mL/10 mL) as well as the enhancement of photo‐induced fluorescence via monomers end‐capped with a phenyl‐[1,3,4]oxadiazolyl moiety threaded with β‐cyclodextrins. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3368–3374, 2010     

Synthesis and characterization of well‐defined cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s and amphiphilic star poly(ε‐caprolactone‐b‐ethylene glycol)s

Per‐2,3‐acetyl‐β‐cyclodextrin with seven primary hydroxyl groups was synthesized by selective modification and used as multifunctional initiator for the ring‐opening polymerization of ε‐caprolactone (CL). Well‐defined β‐cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s (CDSPCLs) with narrow molecular weight distributions (≤1.15) have been successfully prepared in the presence of Sn(Oct)₂ at 120 °C. The molecular weight of CDSPCLs was characterized by end group ¹H NMR analyses and size‐exclusion chromatography (SEC), which could be well controlled by the molar ratio of the monomer to the initiator. Furthermore, amphiphilic seven‐arm star poly(ε‐caprolactone‐b‐ethylene glycol)s (CDSPCL‐b‐PEGs) were synthesized by the coupling reaction of CDSPCLs with carboxyl‐terminated mPEGs. ¹H NMR and SEC analyses confirmed the expected star block structures. Differential scanning calorimetry analyses suggested that the melting temperature (T_m), the crystallization temperature (T_c), and the crystallinity degree (X_c) of CDSPCLs all increased with the increasing of the molecular weight, and were lower than that of the linear poly(ε‐caprolactone). As for CDSPCL‐b‐PEGs, the T_c and T_m of the PCL blocks were significantly influenced by the PEG segments in the copolymers. Moreover, these amphiphilic star block copolymers could self‐assemble into spherical micelles with the particle size ranging from 10 to 40 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6455–6465, 2008