Novel fullerene‐ and polyhedral oligomeric silsesquioxane‐ (POSS) double end‐capped poly(ε‐caprolactone) (PCL) were successfully synthesized. The crystallization behavior of the fullerene‐ and POSS‐ double end‐capped PCL and the effect of aggregation of the POSS and fullerene moieties on the crystallization of PCL were thoroughly studied. The aggregation of the fullerene moieties has much larger confinement effect on the crystallization of PCL than that of POSS. The successful incorporation of two nano‐sized objects, that is, fullerene and POSS, into the PCL matrix may introduce their merits, so that PCL can attain multi‐functional properties.
Fullerene capped poly(ε‐caprolactone)s (PCLs), namely single‐ and double‐fullerene end‐capped PCLs with different fullerene content, were successfully synthesized. The effect of the fullerene end on the crystallization behavior and mechanical properties of the PCL was studied. The aggregation behavior of the fullerene moieties at the end of the PCL chain was also studied. It was found that the aggregated fullerenes have two kinds of effect on the crystallization behavior of the PCL i.e., confinement effect and nucleating effect. The fullerene content shows a certain balance between the confinement effect and the nucleating effect on the crystallization rate of PCL. It was also found that the mechanical properties of the fullerene end‐capped PCLs are strongly related to the content of fullerene and the mode of end‐capping style: either single or double end‐capping.
Atomic force microscopy (AFM) was used for modifying the surface structures of poly(ε‐caprolactone) (PCL) thin film. Oriented growth of PCL crystals at a desired area of the film surface was induced by scanning with a strong, normal load. PCL crystals were first grown edge‐on from the induction line and then their orientation changed to flat‐on at a lamellar length. The effects of molecular weight, crystallization temperature, scanning rate, and normal load on the AFM‐tip‐induced crystallization were examined. The growth kinetics of lamellar crystals in the AFM‐tip‐induced crystallization was the same as that in spherulitic crystallization. It was found that the formation of precursors strongly depends on the applied tip load and is facilitated when the applied load is higher than a threshold.
Maleimido‐terminated PCL (M‐PCL) and alkyne‐terminated PCL (A‐PCL) are prepared by the ring‐opening polymerization of ε‐caprolactone with N‐hydroxyethyl maleimide and 4‐pentyn‐1‐ol as initiators catalyzed by tin(II ) trifluoromethane sulfonate at 25 °C, respectively. A series of saccharide‐terminated PCLs have also been synthesized under mild conditions by two chemical strategies: 1). Michael addition of M‐PCL and amino‐containing maltose, and 2). a ‘click’ reaction of A‐PCL and azide‐containing saccharide. The amphiphilic nature of these maltose‐terminated PCLs make self‐assembly into aggregates in water possible. These aggregates have been characterized by transmission electron microscopy and dynamic light scattering measurements.
Surface patterning was carried out by the epitaxial crystallization of biodegradable PCL on a HOPG, and the surface morphologies were observed by atomic force microscopy. Edge‐on view lamellae were aligned along the HOPG lattice to display stripe patterns in the threefold symmetry. The intervals of stripe patterns composed of ridges and valleys increased with an increase in the crystallization temperature. Enzymatic degradation of the PCL nanopattern allowed the different depth profiles of the fringed structure. The persistence length of the nanopattern could be tuned by the molecular weight of PCL.
Alkynyldextrans with a DS in the range 0.1–1.67 have been prepared as reactive intermediates for further polymer‐analogous functionalisation. DS and substituent distribution were determined by GLC and GLCMS after hydrolysis and acetylation, or methanolysis and trimethylsilylation. Reactivity was in the order O‐2 > O‐4 ≥ O‐3 with pronounced differences in the distinct patterns for propargyl ethers and its higher homologous. A large deviation from a random substituent distribution was observed. Propargyldextrans were not stable during long‐time storage in the solid state, while terminal pentynyl and hexynyl ethers are. Pentynyldextrans showed structure formation of various geometries. They bound silver efficiently, yielding silver nanoparticles by reduction.
Poly(ε‐caprolactone)‐graft‐poly(2‐(dimethylamino) ethyl methacrylate) (PCL‐g‐PDMAEMAs), a kind of amphiphilic graft copolymer, was prepared by combination of ROP and ATRP. The FTIR, 1H NMR, and GPC results indicate that well‐defined polymers with controlled graft density and length of side chain were successfully synthesized. We prepared PCL‐g‐PDMAEMA nanoparticles by employing a nanoprecipitation technique. The pH‐ and thermosensitive properties of PCL‐g‐PDMAEMA nanoparticles were investigated by 1H NMR, TEM, and DLS. It was found that the nanoparticles with an average size of 120 nm presented core–shell structure in aqueous dispersion. Furthermore, the nanoparticles are sensitive to temperature in base while not in an acidic environment.
Poly(ε‐caprolactone) (PCL)/montmorillonite (MMT) nanocomposites were prepared by in situ ring‐opening polymerization of ε‐caprolactone in the presence of MMT modified by hydroxyl‐group containing alkylammonium cation (Cloisite®30B) in a single mode microwave oven. For the polymerization mixtures, plateaus or exothermal peaks were observed in their temperature‐time profiles and can be attributed to the heat‐generating nature of the ring‐opening polymerization. The morphologies of the nanocomposites showed a predominantly exfoliated structure. The mechanical properties of the nanocomposites were evaluated via dynamic mechanical analysis. Compared with that of the recovered PCL matrix, the mechanical properties of the PCL/Cloisite®30B nanocomposites showed obvious improvement.
Two‐dimensional chromatographic methods were developed using LC‐CC in the first and SEC in the second dimension. These methods were applied for the investigation of PS‐b‐PI diblock copolymers synthesized by different approaches: sequential living anionic polymerization and coupling of living precursor blocks. The first dimension separates according to the individual block length of PS or PI blocks, whereas the second dimension separates with respect to the total molar masses of components. 2D‐LC analysis provides information on the purity of the reaction products, the presence of by‐products, the chemical compositions and the molar masses of all product components. The accuracy and selectivity of 2D‐LC is discussed.
Branched α‐olefin 4‐methyl‐1‐pentene (4MP) is polymerized with a cationic α‐diimine palladium catalyst. The influences of polymerization parameters including reaction temperature and monomer concentration on polymer architecture are evaluated in detail. Increasing temperature and lowering monomer concentration can lead to the formation of more complex branched polyolefin because of chain walking. At 0 °C, complex branched polyolefins are generated from quasi‐living polymerization of 4MP with α‐diimine palladium catalyst.
A series of supramolecular degradable inclusion complex (IC) films were formed by threading α‐cyclodextrin (α‐CD) molecules over poly(ε‐caprolactone) (PCL) according to the designed ratio of α‐CD–PCL. Due to containing both α‐CD–PCL inclusion crystallites and uncovered PCL crystallites, the resulting supramolecular α‐CD–PCL IC partial films displayed a shape memory effect. The properties of the materials were investigated by 1H NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and swelling measurement. It was found that the casting temperature and solvent have great influence on the formation and properties of the α‐CD–PCL partial ICs. The modes of complexes on different conditions were proposed. In addition, the introduction of inclusion structure accelerates the degradation of materials strongly.
A series of amphiphilic graft copolymers of poly(ethylene glycol)‐co‐glycidol‐graft‐(ε‐caprolactone) (PEG‐co‐PGL‐g‐PCL) with PEG as the hydrophilic backbone chain and hydrophobic PCL as side chains have been synthesized by living anionic polymerization and ring‐opening polymerization. By changing the composition of the PEG‐co‐PGL backbone chains, and the molar ratio of CL monomer to PEG‐co‐PGL in the feed, copolymers with well‐defined architecture and controllable numbers and length of graft chains can be obtained. The micellization and drug release of the PEG‐co‐PGL‐g‐PCL graft copolymers have been studied in terms of dependence on graft numbers and length, and the results indicate that the micelles with shorter PCL side chains have more compact cores and a relatively small size which are favorable for drug loading and controlled release.
CNT‐induced formation of transcrystals of γ‐PP are reported. Formation of these transcrystals occurred when PP was infiltrated into nanotube aerogel fibers to form polymer nanocomposites. The PP morphology and microstructure with particular focus on the interfacial region of the CNTs were investigated by means of SEM, DSC and WAXD. The transcrystalline supramolecular microstructures were observed around the individual nanotubes during quiescent melting crystallization. Microstructural analysis showed that γ‐form transcrystals of PP dominate the overall interfacial structure. The content of γ‐form transcrystals increased with increase in nanotube loading. The mechanical properties and electrical conductivities of the nanocomposites have been evaluated.
Folic acid conjugation onto poly(1‐vinylimidazole) generates imidazolium copolymers for potential receptor‐mediated nonviral gene delivery. Homopolymer quaternization with various tBoc‐protected bromoalkylamines imparts a permanent charge for DNA complexation. Incorporation of primary amine groups provides a site for folic acid conjugation onto imidazolium copolymers. DNA binding, cytotoxicity, and in vitro transfection in HeLa cells reveal structure–property–transfection relationships for the imidazolium copolymers. Luciferase expression assays establish that primary amine conjugation onto imidazolium copolymers up to 30 mol% fails to improve transfection efficiency. In sharp contrast, incorporation of folic acid onto the copolymers improves transfection efficiency 250‐fold.
Various polyurethane‐based SMPUs were synthesized using five types of polyols as soft segments and two different diisocyanates as hard segments. The effects of diisocyanate concentration on material properties such as crystallinity, transition temperature, shape‐memory effect and tensile strength were investigated. SMPUs with a maximum strain near 1 000%, recovery rate up to ≈98%, fixity up to ≈90% and Tgs of 35–45 °C were obtained. A high MDI content results in SMPUs with better shape‐memory effect, whereas increasing IPDI content leads to a weaker shape‐memory effect. High IPDI concentration seems to prevent or restrict chemical reactions and crosslinks between the polyols and the hard segments, leading to large phase separation and coexistence of soft and hard segments in the macrophases.
ROP of PCL was realized in the presence of mPEG with = 5 000, using Zn(La)2 as a catalyst. The resulting diblock copolymers with molar ratios of the CL/EO repeat units from 0.2–5.0 were characterized by DSC, WAXD, SEC, and 1H NMR. Melt crystallization was studied and analyzed with the Avrami equation. The spherulite growth rate G was determined at different crystallization temperatures. The G values were found to range between those of mPEG and PCL homopolymers. The morphology of an isothermally crystallized sample with CL/EO = 0.5 was examined. Spherulites with PCL embedded in PEG were observed, in contrast to concentric spherulites reported in the literature.
High‐molecular‐weight polythiocaprolactone (PTCL) was prepared in a green process via lipase‐catalyzed ROP of a cyclic 6‐mercaptohexanoic acid (6MH) oligomer. PTCL was readily depolymerized by lipase to cyclic 6MH in dilute toluene solution, which was then readily repolymerized by the same lipase to produce PTCL with the same $\overline {M} _{{\rm w}} $ as the initial PTCL in a chemical recycling process. The Tm of PTCL was higher than that of the corresponding PCL. A P(TCL‐co‐CL) copolymer with 60 mol‐% TCL (6MH) units showed a higher Tm as the PCL homopolymer. Similar apparent Km values were obtained for the cyclic 6MH oligomers and caprolactone oligomers, however, the Vmax of cyclic 6MH oligomers was significantly lower than that of the corresponding caprolactone oligomers.
Preparation of discrete PPPI microspheres was examined using the crystallization of oligomers during isothermal polymerization of PMDA and p‐phenylene diisocyanate, and that of pyromellitic dithioanhydride and PPDA in poor solvents. In contrast to PPPI microspheres with smooth surfaces that were previously prepared by phase‐separation during the polymerization of PPDA and PMDA, the microspheres obtained here consisted of flake‐like lamellae with rugged surfaces. The diameters of the microspheres ranged from 0.5 to 6.7 µm. They exhibited excellent thermal stability depending on the monomers. These results provide a new preparative procedure of the PPPI microsphere with a rugged surface.
The effects of binding ligand variation on the externally initiated Ni catalyzed polymerization of P3HT were investigated using a novel methodology allowing facile screening of ligands. P3HT was synthesized with >80% initiator incorporation for both mono‐ and bidentate phosphine ligands. Variation of the initiating aryl group demonstrated vastly superior results for o‐tolyl over p‐tolyl substituents.
Well‐defined diblock poly(L ‐lactide)‐block‐poly(dimethylamino‐2‐ethyl methacrylate) (PLLA‐b‐PDMAEMA) copolymers were synthesized by combining ROP of LLA and ATRP of DMAEMA, from a dual‐initiator 2‐hydroxylethyl 2‐bromoisobutyrate. The molecular characterization of these diblock copolymers was performed using 1H NMR, FT‐IR, and GPC‐MALLS analysis. The responsive behavior of these diblock copolymers in aqueous solutions at different pH and temperatures were investigated using DLS. Results show that both higher pH and temperature result in a higher degree of neutralization, weaker hydrogen bonding, and micellar aggregation. As observed by TEM, changes in micellar morphology are in accordance with DLS results.
