The kinetics of poly(ethylene terephthalate) melting are studied by DSC and treated in the framework of a nucleation kinetic model. The study focuses on the temperature dependence of the effective activation energy of melting. A theoretical dependence is derived from the model and an experimental one from the Kissinger plot. It is demonstrated that the theoretical dependence satisfactorily predicts the experimental one and fitting the former to the latter can be used for estimating the surface free energy of a nucleus.
Size matters: the interface of nanodroplets in an inverse miniemulsion is used to produce polyphosphate nanocapsules by interfacial polycondensation. Phosphorus acts as a probe for 31P NMR spectroscopy to compare the polycondensation at the nanoscopic droplet with macroscopic interfaces proving less unwanted hydrolysis in miniemulsion by 1H–31P 2D‐heteronuclear multiple bond correlation spectra.
Postfunctionalization is a key tool for the elaboration of hydrophobic surfaces. For that purpose, the elaboration of surfaces suitable for the Huisgen reaction allows for functionalization with various hydrophobic side chains. Here the synthesis of azido or alkyne monomers is reported to prepare platform surfaces suitable for click chemistry. The surface hydrophobicity and morphology are investigated. Superhydrophobic and parahydrophobic properties are obtained depending on the starting monomer and the molecule used for the postfunctionalization.
An investigation of the structure–property relationships of poly(dimethyl siloxane) (PDMS) polyoxamide segmented copolymers reveals the impact of oxamide spacing and PDMS molecular weight on physical properties. Varying the length of the methylene spacing between the oxamide hydrogen bonding groups in the hard segment (HS), as well as the PDMS soft segment molecular weight, provides insight into the influence on thermal and mechanical properties. Bulk polycondensation of ethyl‐oxalate‐terminated PMDS oligomers with diamines yields optically clear, thermoplastic elastomers with excellent mechanical properties. The structure–property investigation reveals optimum mechanical properties of PDMS polyoxamide segmented copolymers occur with the smallest spacing between oxamide groups in the HS.
The synthesis of high‐aspect‐ratio (AR) CdSe (NRs) nanorods and their ordered assembly over large areas are reported. Long‐range ordering of hexagonal arrays of high‐AR NRs is achieved by a combination of controlled solvent evaporation and the use of an applied electric field. Vertically oriented assemblies of CdSe NRs functionalized with oligo‐ and polythiophene are also obtained. Aligned and oriented polythiophene CdSe NRs have potential applications in organic–inorganic hybrid bulk‐heterojunction photovoltaic devices.
The preparation and study of a new poly(3‐alkyloxythiophene)—bearing a chiral center—is presented, with particular reference to the evolution of optical activity in passing from solution to solid state. The combination of optical analysis, electronic circular dichroism, and X‐ray diffraction of powders or films supplies strong indications of a possible use of this material as an inverse chiral probe.
The swelling of poly(acrylic acid) brushes in aqueous solutions is studied by neutron reflectivity. The brushes are synthesized on silicon wafers using a “grafting onto” approach and their stretching is investigated at various pH, grafting densities, and chain lengths. Neutron reflectivity provides the average thickness and, more interestingly, the density profile of the brushes. The profiles obtained experimentally are in good agreement with theory. The swelling ratio of the poly(acrylic acid) brushes is compared with that of other polymer brushes formerly investigated using classic scaling laws. Owing to a new representation with the normalized thickness, it is demonstrated that there is a general behavior for all polymer brushes with a master curve for neutral polymer brushes and for polyelectrolyte brushes.
Nonionic aliphatic polymers containing ester and sulfonyl moieties, [poly(ester‐sulfones)s] were found to undergo anode‐selective electrophoresis under electrophoretic deposition conditions. Herein are reported the syntheses of unsaturated nonionic polyesters containing sulfide linkages and double bonds on the polymer backbone via acyclic diene metathesis polymerization using a Grubbs' catalyst. Subsequent oxone oxidation was carried out, affording the corresponding poly(ester‐sulfone), followed by electrophoretic deposition of the unsaturated poly(ester‐sulfone) onto stainless steel. Subsequent UV‐irradiation cured the deposited film, improving the peeling strength of the coating.
Core–corona inversion of micelles of diblock copolymer poly(acrylic acid)‐block‐poly(N‐isopropylacrylamide) (PAA‐b‐PNIPAM), has been successfully realized by switching either pH or temperature. The strong interaction of doxorubicin with the PAA block and the pH‐sensitive drug release from the polymer make the system very useful as a controlled drug delivery system. The encapsulation of hydrophobic Nile Red molecules above the lower critical solution temperature of PNIPAM suggests that this polymer may be useful for removing hydrophobic pollutants.
Sub‐micrometer spheres of poly(glycidyl methacrylate) (PGMA) with a layer of poly(allylamine hydrochloride) (PAH) film are prepared by an easily controlled assembly method. The gold nanoparticles (Au NPs) exhibit a discontinuous structure on the PGMA@PAH particle surface, exhibiting a surface interaction between the PGMA spheres and the Au NPs. PAH not only modifies the surface of the PGMA particles but also affirmatively affects the crystallite of the PGMA particles. The real permittivity of the nanocomposite spheres is much higher than that of pure PGMA spheres. An improved thermal stability is observed in the nanocomposite spheres. The calculated bandgap (0.91 eV) of the nanocomposite spheres is observed to be lower than that (4.92 eV) of pure PGMA spheres.
As polypeptoids become increasingly popular, they present a more soluble and processable alternative to natural and synthetic polypeptides; the breadth of their potential functionality slowly comes into focus. This report analyzes the ability of an alkyne‐functionalized polypeptoid, poly(N‐propargyl glycine), to crosslink upon heating. The crosslinking process is analyzed by thermal analysis (differential scanning calorimetry and thermogravimetric analysis), Fourier‐transform infrared, electron paramagnetic resonance, and solid‐state NMR spectroscopy. While a precise mechanism cannot be confidently assigned, it is clear that the reaction proceeds by a radical mechanism that exclusively involves the alkyne functionality, which, upon crosslinking, yields alkene and aromatic products.
Thermally reduced graphene modified with cationic ammonium ions (AAG)—affording a stable dispersion in water—self‐assembles well by electrostatic interaction on the surface of anionic poly(methyl methacrylate) (PMMA) particles of various sizes, by simple mixing in water. An interconnected 3D electrically conductive network of AAG is effectively generated in the composite when the self‐assembled composite is compression molded. The AAG network becomes wide‐meshed and electrical conduction is improved when the PMMA particle size increases, exhibiting a percolation threshold of electrical conductivity as low as 0.06 vol%. In contrast, the protection of PMMA from oxidation by air is more effective when the network is fine‐meshed.
Polymer blends play a significant role in polymer science due to their new and unique properties compared with the individual polymer components. However, most polymer blends are immiscible and not adaptive to environmental stimuli. Here, an enhancement of the compatibility of an immiscible poly(methy acrylate)/polystyrene blend based on multiple‐responsive benzo‐21‐crown‐7/dialkylammoniumsalt host–guest interactions is made. Owing to the multi‐responsiveness and reversibility of benzo‐21‐crown‐7/dialkylammoniumsalt host–guest interactions, the polymer blend recovers its compatibility after being damaged by environmental factors, indicating its adaptiveness.
Lamellar bending habits, as influenced by molecular‐chain chirality, in packing into dendritic spherulites with specific optical patterns are discussed using two model polymers of opposite chirality that are blended with a common polymer as examples: i) poly(l ‐lactic acid)/poly(butylene adipate) (PLLA/PBA) and ii) poly(d ‐lactic acid)/PBA (PDLA/PBA) blends. The bending habits in the spherulites of PLLA or PDLA blended with PBA are dictated by the chirality, specifically the counterclockwise and clockwise directions for the PLLA/PBA (50:50) and PDLA/PBA (50:50) blends, respectively. Straight lamellae in spiral lozenge crystals are packed with crystal aggregates of PLLA on top of the flat‐on lamellae plates acting as a basal plane during crystallization at Tc; spiral lozenge‐crystal frameworks are surrounded by needle‐like crystals resembling PBA crystals.
A first‐principles map for the equilibrium morphologies of polymer–inorganic nanocomposites synthesized by miniemulsion polymerization is developed. The predictions are compared with literature results on the effect of the initiator type, surfactant concentration, monomer system, and surface characteristics of the inorganic nanoparticles on the morphology of the nanocomposites. The limitations of the morphology map are also discussed.
The synthesis and electrochemical properties of four electropolymerizable monomers featuring an interior aromatic diamide or diimide segment bridged by p‐phenylene units to terminal electroactive carbazole groups are described. Upon electrochemical oxidation, the coupling reactions between carbazole radical cations occur instantly, rendering an efficient electropolymerization process feasible. The electrogenerated polymer films exhibit reversible electrochemical processes and stable color changes upon electro‐oxidation, which can be switched by potential modulation. The remarkable electrochromic behavior of the film is clearly interpreted on the basis of spectroelectrochemical studies.
Unsaturated polyesters are synthesized via ring‐opening copolymerization of α‐methylene‐δ‐valerolactone and δ‐valerolactone. These polyesters 4a–c are mixed with ethyl methacrylate (EMA), 2‐hydroxyethyl methacrylate (HEMA), and α‐methylene‐δ‐valerolactone (α‐MVL), respectively. Then, crosslinking is carried out by free radical polymerization initiated by an azo‐initiator. A second glass transition is found with incorporation of HEMA and α‐MVL. These findings indicate the formation of phase‐separated polyester blocks crosslinked with the poly(meth)‐acrylic‐segments, respectively poly(α‐methylene‐δ‐valerolactone) segments.
Highly monodisperse poly(2‐hydroxyethyl acrylate)‐grafted poly(methyl methacrylate) (PMMA) microspheres are prepared by a facile photoinitiated dispersion polymerization in ethanol/water mixtures at room temperature. Poly(2‐hydroxyethyl acrylate) homopolymers with different molecular weights are synthesized via reversible addition‐fragmentation chain transfer (RAFT) solution polymerization and employed as steric stabilizers in photoinitiated dispersion polymerization. The effect of macro‐RAFT agent (both concentration and molecular weight) on particle diameter is studied in detail. Kinetic study indicates that the polymerization proceeded rapidly with 96% yield being reached with 1 h of UV irradiation. Finally, the obtained hydroxyl‐rich PMMA microspheres are used as building blocks for the preparation of covalently cross‐linked colloidosomes.
A series of brominated polystyrenes (BPSs) are readily synthesized and blended as polymer dopants with the p‐type semiconducting polymer, poly(3‐hexylthiophene) (P3HT), to improve theirelectrical performance. The obtained P3HT/BPS blend films exhibit increased carrier concentration resulting from doping of P3HT by BPS, which leads to excellent electrical performance, including enhanced hole mobility and conductivity, and the conductivity or mobility increases with the bromination degree of BPS. Compared with conventional small molecular dopants, the polymer dopant, BPS, shows not only excellent doping stability, but also good solution processibility, which makes it a promising materials for fabrication of low cost, flexible, transparent, and high performance solution processable organic electronic devices.
This work aims to improve the outstanding thermal and mechanical properties of commercialized wholly aromatic polyamide fibers (i.e., aramids), by crosslinking the materials. The introduction of a reactive azide group into the polymer structure leads to functional aramids. Crosslinking processes can be easily performed using an inexpensive thermal treatment after fiber spinning with current spin production facilities.
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