New polyhydrazides and poly(amidehydrazide)s bearing redox‐active carbazole and triphenylamine units were prepared. The resulting poly(1,3,4‐oxdiazole)s and poly(amide‐1,3,4‐oxadiazole)s had high glass‐transition temperatures (288–330 °C) and high thermal stability. The dilute solutions of all the hydrazide and oxadiazole polymers showed a weak–medium photoluminescence with emission maxima around 474–506 nm. The polymer films revealed two well‐defined and reversible redox couples upon electrochemical oxidation, together with interesting electrochromic behaviors. They showed enhanced redox‐stability and electrochromic performance. CV of the oxadiazole polymers also showed reduction processes due to the formation of radical anions of the oxadiazole units.
The nanocrystalline structure of thermally annealed P3HT ultrathin films was studied as a function of the substrate properties using AFM, GIXRD, and static contact angle measurements which showed that an edge‐on structure is formed on both types of substrate. Substrate‐induced ordering is observed at the interface with air only when the film matches the average lamellae thickness, ≈30 nm in the present case, while, when the film thickness is higher than a single lamella size, i.e., ≈60 nm the substrate nature does not affect the lamellar ordering at the film/air interface. In other words, the substrate properties seem able to induce the ordering of the only first crystalline layer. These results are discussed in terms of simple relationships between interface free energy and chain mobility.
Kinetic investigations on the cationic ring‐opening polymerization of 2‐ethyl‐2‐oxazoline were conducted using acetyl chloride, acetyl bromide, and acetyl iodide as initiators. Various polymerization temperatures ranging from 80 to 220 °C were applied under microwave irradiation. The resulting polymerization mixtures were characterized with GC and GPC for the determination of monomer conversion and molecular weight distribution, respectively. Well defined polymers with narrow molecular weight distributions ( = 6 000 Dalton, PDI ≈ 1.10) were obtained with all three initiators.
Pressure‐volume‐temperature and surface tension behaviour were studied for random copolymers of styrene and acrylonitrile (SAN) and for poly(butylene terephthalate) (PBT). Results served to determine reduction parameters for the equation‐of‐states by Flory‐Orwoll‐Vrij and by Simha‐Somcynsky as well. Surface tension as a function of copolymer composition displays negative deviation from additivity. It indicates surface excess of styrene units. Similar behaviour with respect to copolymer composition was found for variation of interfacial tension between SAN and PBT. Thickness of surface region is around 1 nm and does not change with copolymer composition whereas extension of interfacial region between PBT and SAN copolymers varies strongly with copolymer composition between around 2 and 60 nm.
Graft‐type anion‐conducting polymer electrolyte membranes (AEMs) are prepared by the radiation‐induced graft polymerization of chloromethylstyrene into poly(ethylene‐co‐tetrafluoroethylene) (ETFE) films and subsequent quaternization with trimethylamine. AEMs in the hydroxide form (AEM‐OH) are prepared by immersing the chloride form (AEM‐Cl) in 1 M potassium hydroxide (KOH) solution, followed by KOH and washing with nitrogen‐saturated water to prevent bicarbonate formation (AEM‐HCO3). The AEM‐OH shows conductivity and water uptake four and two times higher than AEM‐Cl and ‐HCO3 and is thermally and chemically less stable, resulting in the tendency to absorb water and to convert to the bicarbonate form.
Ethyl cellulose‐graft‐poly(2‐hydroxyethyl methacrylate) (EC‐graft‐PHEMA) graft copolymers were synthesized by atom‐transfer radical polymerization (ATRP) in methanol. The graft copolymers were characterized by means of gel‐permeation chromatography (GPC) and 1H NMR spectroscopy. The kinetic study indicated that the polymerization was controllable. The EC‐graft‐PHEMA copolymers self‐assembled in water into spherical micelles. The morphology of the micelles was characterized by dynamic light scattering (DLS) and transmission electric microscopy (TEM) and the formation process of the micelles was discussed.
PLLA/PDLA blends were crystallized between 120 and 195 °C. The stereocomplex spherulites acquired in equimolar and non‐equimolar blends were compared using POM, WAXD, DSC, and AFM. For equimolar blends, stereocomplex crystals show spherulites with positive birefringence, which is ascribed to the existence of domains made up of tangentially oriented lamellae. For PLLA‐rich (or PDLA‐rich) blends, the signs of the birefringence changed from a positive spherulite to a mixed spherulite and then to a negative spherulite. In negative spherulites, most lamellae orient radially. Radial and tangential cracks were observed in equimolar blends when crystallization took place above 175 °C whereas no cracks formed for non‐equimolar blends.
A novel tertiary amine and amino acid‐based “schizophrenic” pH‐responsive block copolymer, PDEA‐b‐PAP, has been synthesized by RAFT polymerization. By directly dissolving this copolymer in acid or basic aqueous solution block copolymer vesicles with switchable coronas and membranes were prepared. These novel assemblies were characterized using TEM, DLS, zeta potential, and SLS analysis.
Colloidal nanosized folate‐conjugated hydrogels for targeted chemotherapy were prepared via a versatile and efficient postsynthetic modification pathway starting from P(NPA‐co‐NIPAM). The modifications included the introduction of 4‐methylpyridine as pH‐sensitive pendant groups and the conjugation of folic acid to the microgel network. The microgels showed a specific swelling at pH < 6 (endosomes) as judged by DLS studies varying the external pH. The relative composition of the microgels shows a clear influence on the pH volume transition shifting. The potential of the microgels for anticancer drug release at pH = 5.0 was confirmed. Therefore, they are a promising targeting carrier for improved anticancer chemotherapy.
The synthesis of branched polyols from glyceryl triundec‐10‐enoate by acyclic triene metathesis polymerization (ATMET) is reported. 10‐Undecenol is used as a monofunctional comonomer to end‐cap polymer chains, functionalize the periphery of the resulting branched materials, and to control the molecular weight. The thus obtained castor oil derived polyols are reacted with 4,4′‐methylenebis(phenylisocyanate) (MDI) to yield a series of semicrystalline polyurethane networks. The investigation of the thermal stability and the thermomechanical and mechanical properties of these thermosets revealed good shape memory properties.
Linking PEG2,000 polymers ending in 1 or 2 carboxylic groups to lipoamino acids (LAAs) gives mono‐ and homo‐disubstituted PEG‐LAA conjugates. They show an identical solubility to parent PEGs in water and organic solvents. By DSC the degree and depth of interaction of these conjugates with a biomembrane model is studied, gaining information about their future incorporation in drug‐loaded nanocarriers. The ability of PEG‐LAA conjugates to adopt an ordinate arrangement on the surface of particles and efficiently cover them is demonstrated, compared to DSPE‐PEG, by measuring the zeta potential values of negatively charged liposomes prepared in their presence.
Terpyridine‐modified hydrophobic poly(dimethylsiloxane) and hydrophilic poly(ethylene oxide) were combined to new metallo‐supramolecular AB‐diblock copolymers by utilizing Ru(II) ions. The polymers were synthesized by hydrosilylation of heteroleptic allyloxy‐functionalized Ru(II) complexes. The amphiphilic AB‐diblock copolymers were used to prepare micelles in an aqueous environment, which were subsequently characterized by dynamic light scattering and cryogenic transmission electron microscopy.
Non‐natural amino acids can be used to expand the protein sequence space significantly beyond the limits set by nature. Expanding the protein sequence space opens a new door to engineering and chemically modifying proteins. Reassigning codons to non‐natural amino acids as well as engineering protein translational machinery is required to incorporate non‐natural amino acids into a single or multiple sites of a target protein in cells. Non‐natural amino acid incorporation holds a great promise in substantially improving protein intrinsic properties and providing new orthogonal chemistries to proteins for bioconjugation.
During characterization of a temperature‐responsive poly(N‐isopropylacrylamide) (PIPAAm) layer grafted onto a Si(100) substrate, atomic force microscopy (AFM) is able to probe the interactions between the microscope tip and the polymer. The modification of the AFM tip surface with octadecyltrichlorosilane (OTS) changes the interaction between the PIPAAm surface and the tip. Although a repulsive interaction is observed between a commercially available Si tip and the PIPAAm surface, a strong attractive interaction between the OTS‐modified Si tip and the surface is observed. Adhesion‐force analysis shows changes in the hydrophilic/hydrophobic character of ultrathin PIPAAm surfaces immediately after a change in temperature. The PIPAAm surface becomes hydrophobic less than 30 min after temperature increase, but requires 120 min to become hydrophilic after temperature reduction.
The amphiphilic triblock copolymer PLA‐b‐PLL‐b‐MPEG is prepared in three steps through acylation coupling between the terminal amino groups of PLA‐b‐PZLL‐NH2 and carboxyl‐terminal MPEG, followed by the deprotection of amines. The block copolymers are characterized via FT‐IR, 1H NMR, DSC, GPC, and TEM. TEM analysis shows that the triblock polymers can form polymeric micelles in aqueous solution with a homogeneous spherical morphology. The cytotoxicity assay indicates that the final triblock polymer micelles after deprotection show low cytotoxicity against Bel7402 human hepatoma cells. MPEG and PLL were introduced into the main chain of PLA affording a kind of ideal bioabsorbable polymer materials, which is expected to be useful in drug and gene delivery.
Nanoscale thin films of PVDF containing the β‐crystalline phase were directly prepared by heat‐controlled spin coating without the influence of external stimuli either in the form of additives or post‐treatments. Sample preparation was carried out at different temperatures, ranging from 10 to 70 °C. At elevated temperatures (40, 50, 60 and 70 °C), PVDF was crystallized into the β‐phase, while at near‐ambient conditions (20 and 30 °C) it was crystallized into the α‐phase. Some samples exhibited a phase‐segregated morphology, with varying particle sizes depending on the preparation temperature. The ferroelectric nature of a typical sample, prepared at 40 °C, was visualized by piezoresponse imaging studies.
P2VN‐b‐PAA is a novel diblock copolymer which has potential as a self‐assembled nanoscale patterning material. Thin spin cast P2VN‐b‐PAA films rapidly reorganize to vertical lamellar with exposure to acetone vapor. P2VN‐b‐PAA lamellar morphology was aligned by electric field under acetone vapor at a significantly faster rate and at lower electric field strengths than other polymer systems. Observed dry etching selectivity for P2VN to PAA were comparatively high for a variety of etch gases, consistent with estimations from Ohnishi and ring parameters. Block copolymer self assembled patterns were transferred to silicon via two‐step CF4 and SF6 etching.
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.
New polydimethylsiloxanes with p‐substituted azobenzene side‐groups were synthesized. Thin films and solutions exhibit a photochemical trans‐cis isomerization of the azobenzene groups, followed by their cis‐trans thermal relaxation in the dark. In films, relaxation rates were found to be 100–1 000 times slower than the rates of photoisomerization, the former being very sensitive to the electron‐acceptor character of the substituents. in solution, the rates of cis‐trans relaxation are lower than those obtained for the solid state. This is ascribed to the dipolar intramolecular interactions between cis chromophores, which are favored in solution.
Biodegradable supermacroporous PHEMA cryogels were produced by combining two crosslinkers, poly(ethylene glycol) diacrylate and a newly developed disulfide water soluble crosslinker, N,N′‐bis(methacryloyl)‐L ‐cystine. The biodegradable PHEMA cryogels were prepared with gel fraction yields up to 70% and were characterized by highly interconnected pores of micrometer size and good mechanical stability. When subjected to reductive agents like DTT, the biodegradable PHEMA cryogels disintegrated into small pieces. The rate of disintegration was controlled by the crosslinking density in the cryogels and the DTT concentration.
