A novel approach is employed to produce core–corona nanospheres, which introduces a stereoregular hydrophilic part to an amphiphilic block copolymer. The resultant morphology is reported using isotactic‐poly(methacrylic acid)‐block‐poly(butyl acrylate). Infrared spectroscopy revealed a supramolecular interaction, and X ray diffraction revealed the crystallization of the outer isotactic‐poly(methacrylic acid) part. The nanostructure, which looks like a nanosized ‘grape’, was formed when nanospheres and nanofibers coexisted simultaneously and partially fused.
This communication details the successful synthesis of low polydispersity core cross‐linked star (CCS) polymers via DPE‐mediated polymerisation. We demonstrate the ability to produce poly(methyl methacrylate) and poly(acrylonitrile) CCS polymers that are currently inaccessible via the two most common non‐metal‐based controlled radical polymerisation techniques (NMP and RAFT polymerisations).
The phase diagram of a series of poly(1,2‐octylene oxide)–poly(ethylene oxide) (POO–PEO) diblock copolymers is determined by small‐angle X‐ray scattering. The Flory–Huggins interaction parameter was measured by small‐angle neutron scattering. The phase diagram is highly asymmetric due to large conformational asymmetry that results from the hexyl side chains in the POO block. Non‐lamellar phases (hexagonal and gyroid) are observed near fPEO = 0.5, and the lamellar phase is observed for fPEO ≥ 0.5.
The intracellular delivery of Doxorubicin (Dox) from poly(lactide‐co‐glycolide) (PLGA) nanoparticles stabilised with bovine serum albumin, in HepG2 cells, is studied via flow cytometry, fluorescence lifetime imaging microscopy (FLIM), confocal Raman microscopy (CRM) and cell viability studies. Flow cytometry shows that the initial uptake of PLGA and Dox follow the same kinetics. However, following 8 h of incubation, the fluorescence intensity and cellular uptake of Dox decreases, while in the case of PLGA both parameters remain constant. FLIM shows the presence of a single‐lifetime species, with a lifetime of 1.15 ns when measured inside the cells. Cell viability decreases by approximately 20% when incubated for 24 h with PLGA loaded with Dox, with a particle concentration of 100 µg · mL?1. At the single‐cell level, CRM shows changes in the bands from DNA and proteins in the cell nucleus when incubated with PLGA loaded with Dox.
Summary: A highly fluorescent photochromic polymer, poly‐BTFO4, was prepared. The fluorescence quantum yield of the poly‐BTFO4 was six times higher than that of BTFO4. Fatigue resistance of the polymer at its photostationary state was significantly enhanced compared with that of BTFO4. Importantly, the poly‐BTFO4 film also showed an efficient photochromism as well as strong fluorescence similar to the results in solution, which allow photoinduced fluorescence switching applicable to optical switches.
Improvement of fluorescence quantum yield and fatigue resistance. 相似文献
A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with reprocessability restricted to physically crosslinked SMPs is demonstrated by covalently bonding, through thermoreversible Diels–Alder (DA) adducts, star‐shaped poly(ε‐caprolactones) (PCL) end‐functionalized by furan and maleimide moieties. A PCL network is easily prepared by melt‐blending complementary end‐functional star polymers in retro DA regime, then by curing at lower temperature to favour the DA cycloaddition. Such covalent network can be reprocessed when heated again at the retro DA temperature. The resulting SMP shows still excellent shape memory properties attesting for its good recyclability.
Summary: Copolymers of poly(ethylene oxide) (PEO) and 5,5′‐azodisalicylic acid (Olsalazine, OLZ) were synthesized and evaluated by hydrolysis and in‐vitro biodegradation with azoreductase. It was found that changing the molecular weight of the PEO blocks affected the loading ratio of OLZ, and resulted in significant differences in the hydration and degradability of the copolymers. These novel azo‐containing copolymers can be used in colon‐specific drug delivery.
Release of 5‐ASA from OLZ and PEO‐OLZ copolymers incubated with rat cecum content in the presence of benzyl viologen and α‐D ‐glucose. 相似文献
The preparation of polypyrrole/Fe3O4 nanospheres by a facile mini‐emulsion polymerization method is investigated using poly(ethylene glycol), poly(ethylene oxide), poly(vinyl alcohol), and hyaluronic acid as surfactants. Hyaluronic acid is deemed the most suitable surfactant since it results in well‐dispersed nanospheres of 80–100 nm, and offers the advantages of biocompatibility, cell adhesive property, and the availability of functional groups for attachment of other molecules. These polypyrrole/Fe3O4 nanospheres are magnetic and can be further functionalized with a cancer antibody, herceptin. Our results show that this combination of hyaluronic acid and herceptin results in high specific uptake of the nanospheres by cancer cells.
Summary: New polymer gelators consisting of poly(propylene glycol) or poly(ethylene glycol) and L ‐lysine‐based low‐molecular‐weight gelators have been developed. These polymer gelators were synthesized according to a simple procedure with high reaction yield, and formed organogels in many organic solvents. The organogelation mechanism was proposed from the transmission electron microscopy and FTIR spectroscopy studies.
Structures of the polymer gelators synthesized here. 相似文献
Summary: We demonstrate a novel approach for constructing photoactive multilayer films in which the aggregation of fluorescing molecules is effectively eliminated. In the films formed via a layer‐by‐layer electrostatic self‐assembly technique, the core‐shell amphiphilic copolymer, poly[(sodium 4‐styrenesulfonate)‐block‐vinylnaphthalene], was deposited. The isolated cores served as nanosized host sites for photoactive guest molecules (pyrene, perylene). The efficient energy transfer between polymeric chromophores and perylene molecules was observed.
AFM image of a nanostructured polymeric film prepared via a layer‐by‐layer technique and containing photoactive block copolymer poly[(sodium 4‐styrenesulfonate)‐block‐vinylnaphthalene]. Below is the representative height profile taken along the drawn line. 相似文献
Crystallization of poly(2‐isobutyl‐2‐oxazoline) and poly(2‐nonyl‐2‐oxazoline) is found to occur by room temperature annealing below the upper critical solution temperature in ethanol–water solvent mixtures. Both polymers produce similar self‐assembled structures (see image), resembling the previously reported crystalline hierarchical structures obtained from hot aqueous poly(2‐isopropyl‐2‐oxazoline) solutions above the lower critical solution temperature. These observations suggest that the crystallization induced self‐assembly process is a rather general phenomenon occurring for semicrystalline polymers in liquid–liquid two phase systems.
Three synthesis lots of linear poly(ethyleneimine) (PEI) are compared to a fully hydrolyzed linear PEI (commercially available as PEI “Max”) regarding structure, polyplex formation with plasmid DNA, and transfection of suspension‐adapted HEK‐293E cells. PEI “Max” binds DNA more efficiently than the other PEIs, but it is the least effective in terms of transient recombinant protein yield. One PEI lot is fractionated by means of SEC. The fractions of high‐$\overline {M} _{{\rm n}} $ PEI are the most efficient for complex formation and transfection. Nevertheless, the highest transient recombinant protein yields are achieved with unfractionated PEI. The results demonstrate that the polydispersity and charge density of linear PEI are important parameters for gene delivery to suspension‐adapted HEK‐293E cells.
Self‐doped sulfonated polyaniline (PSA) has been synthesized on the surface of micellar nanoparticles made from positively charged surfactants by biocatalysis. The conformation forced by the electrostatic charge interactions between the positively charged micelle and the negatively charged PSA increases the conductivity of the PSA by three orders of magnitude. The pure PSA recovered from ion exchange, however, shows quite similar electrical properties compared with sulfonated polyanilines reported earlier. The increased conductivity of PSA complexes is as a result of the increased charge carrier concentration caused by a certain conformational locking.
Summary: The microstructure and phase transformation of a highly‐branched polyethyleneimine/octadecanoic acid (PEI(OA)1.0) complex were investigated using a combination of DSC, XRD, optical polarised microscopy and temperature dependent FT‐IR spectroscopy. A mesogen‐free thermotropic liquid crystalline state was observed in a certain temperature region. The strong ionic interaction between COO− (from OA) and NH (from PEI) and the hydrophobic interaction between the alkyl side chains contributes to the formation of a thermotropic liquid crystalline structure.
This work reports on thermally tunable surface wettability of electrospun fiber mats of: polystyrene (PS)/poly(N‐isopropylacrylamide) (PNIPA) blended (bl‐PS/PNIPA) and crosslinked poly[(N‐isopropylacrylamide)‐co‐[methacrylic acid)] (PNIPAMAA) (xl‐NIPAMAA). Both the bl‐PS/PNIPA and xl‐PNIPAMAA fiber mats demonstrate reversibly switchable surface wettability, with the bl‐PS/PNIPA fiber mats approaching superhydrophobic ≥150° and superhydrophilic contact angle (CA) values at extreme temperatures. Weight loss studies carried out at 10 °C indicate that the crosslinked PNIPAMAA fiber mats had better structural integrity than the bl‐PS/PNIPA fiber mats. PNIPA surface chemistry and the Cassie–Baxter model were used to explain the mechanism behind the observed extreme wettability.
Microporous films consisting of two‐dimensionally ordered void structures ‐ so‐called honeycomb films ‐ were produced by evaporation of polymer solutions under high humidity. Two types of poly(vinyl cinnamate)s were used: A newly synthesized amphiphilic poly(vinyl cinnamate) and a mixture of a commercial poly(vinyl cinnamate) and an amphiphilic polyion complex. Photo‐crosslinking of the honeycomb structure could be achieved by UV irradiation while completely retaining the film morphology. The crosslinked films showed excellent stability against organic solvents.
