A facile approach to the preparation of functionalized polymeric nanoparticles with UV‐crosslinkable core and bromine‐bearing shell has been developed from the polymerization‐induced self‐assembly of the block copolymers PBNBE‐b‐PCONBI and PBNBE‐b‐PCONBI‐b‐PONBDM. The block copolymers were characterized by means of 1H NMR and GPC. The polymeric nanoparticles with a fixed shell length and varied core lengths were obtained through the control of the molar ratio of monomers in the feed. The micelles were crosslinked using UV‐irradiation, and the characteristics of the polymeric nanoparticles in toluene, THF, or CHCl3 before and after UV irradiation were investigated by means of DLS, UV‐Vis, GPC, AFM, and TEM.
A novel acid‐cleavable diacrylate crosslinker, DCDA, was used as a difunctional Michael acceptor in the synthesis of acid‐cleavable crosslinked networks via base‐catalyzed Michael addition of telechelic poly(ethylene glycol) bis(acetoacetate). Michael addition networks containing DCDA were degraded in the presence of catalytic quantities of acids to form soluble polymeric products. Michael addition networks of non‐degradable diacrylate crosslinkers were chemically unchanged under identical reaction conditions and remained insoluble. Thermal degradation of DCDA‐containing networks was also investigated using TGA, which confirmed the thermal reactivity and concentration of the acid‐labile crosslink points.
New thermo‐sensitive functionalized graft copolymers characterized by a poly(N‐isopropylacrylamide) backbone and grafts containing 2‐ethyl‐2‐oxazoline and 2‐(2‐methoxycarbonylethyl)‐2‐oxazoline units were synthesized. The conformation transition temperatures of the graft copolymers could be modified by variation of the molar composition in the side chain, by different side chain structure (random distribution of both oxazolines vs. diblock structure) and by hydrolysis of the methylester to the acid form. Graft copolymers with long functional oxazoline side chains allowed the stabilization of aggregates above the phase transition temperature of the backbone until the LCST of the side chain. The temperature window allowing for the formation of stable aggregates was widened with acid functions in the corona.
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.
N‐isopropylacrylamide (NIPAM) is photopolymerized in a range of phosphonium‐based ionic liquids (ILs). The curing behaviour of polymer‐IL solutions (linear pNIPAM) and ionogels (crosslinked pNIPAM) is studied using rheometry, DSC, and GPC. It is found that the IL influences the mechanical properties, the rate of polymerization, and the LCST of the resulting pNIPAM ionogels. Ionogels made in trihexyl‐tetradecyl phosphonium dicyanamide show an order of magnitude smaller ratio of loss/storage moduli compared to that of trihexyl‐tetradecyl phosphonium chloride, and a doubling of the UV polymerization rate. Temperature‐ramp rheology scans of the water‐swollen ionogels show that upon LCST transition the moduli of the polymer network exhibit anion dependent increases.
AFM imaging was used to investigate the influence of molecular structure and composition on the formation of Langmuir monolayers by arborescent PS‐graft‐PEO copolymers at the air/water interface. Even without compression, these molecules associate spontaneously at the air/water interface and form stable monolayers that are easily transferred onto solid substrates as Langmuir/Blodgett films. The copolymers either form aggregates with a low association level, large island‐like clusters, or ribbon‐like superstructures. The different behaviors of the copolymers are rationalized in terms of the influence of their composition and of the structure of the arborescent PS cores on the assembly process.
Nanoprecipitation of poly(methyl methacrylate) (PMMA) in the presence of water‐soluble core cross‐linked star (CCS) polymers is investigated. Slowly dropping water into DMF solutions containing PMMA and CCS polymers of varying compositions produces colloidally stable particles with CCS polymers being effectively incorporated. During the solvent‐shifting process, CCS polymers migrate to and concentrate at the particle surface to stabilize the formed particles, which is confirmed by X‐ray photoelectron spectroscopy, transmission electron microscopy, and contact angle measurements. This stabilizing effect is realized via the steric effect of the CCS polymers adsorbed at the particle surface.
A series of SGPs composed of a PLL main and a PLGA side chain was synthesized with different DSs in a DMSO solvent. The addition of water induced the self‐assembly of PLL/PLGA SPGs into spherical micelles. The size of the spherical micelles decreased with an increase in DS and core/shell structures, which was confirmed by XPS and zeta‐potential measurements. The morphological transitions were under thermodynamic control when the solvents mixed. Consequently, further increases in water content caused the transition of the spherical micelles to vesicles, while the initial spherical micelles were reconstructed from vesicles when the DMSO was added. The content of water, the boundaries for the morphology transition, depended on the DS. pH and salt levels affected the stability of the aggregates.
Fluorescent cellulose derivatives were synthesized by utilizing the carbazole group in order to induce optical and semi‐conducting properties. The PL spectra of these cellulose derivatives exhibit UV‐blue emissions at about 350–450 nm attributed to carbazole groups. Analyses of photoelectron spectra were also performed to determine IP values. The results of IP, UV‐vis and PL analyses were almost the same as those of PVK, while the PL intensity and efficiency of the cellulose derivatives were quite different. These compounds functioned as hole transporting materials of OLEDs. Devices using each of the derivatives showed different electronic behavior (current density‐voltage characteristics, EL spectra, etc.), indicating the importance of regioselectivity of the substituent group.
The synthesis of linear polyethyleneimine (LPEI) by acidic hydrolysis of poly(2‐ethyl‐2‐oxazoline) is studied and optimized to reach the highest degree of hydrolysis within the shortest time range using a microwave synthesizer. In addition, the purification procedure is significantly improved; the fast batch processing combined with an excellent control of the actual heating time represents a well‐suited alternative to the conventional synthesis on the way to “pharmagrade” PEI. The developed protocol for the preparation of methyl and proton‐initiated LPEIs shows a high reproducibility, and the identity and purity of the LPEIs is proven by means of 1H NMR and IR spectroscopy as well as MALDI‐TOF‐ and ESI‐Q‐TOF‐MS.
The Diels–Alder reaction of furan and maleimide is used to prepare reversibly cross‐linking polymer gels consisting of furan‐bearing polymer chains and bismaleimides. The roles of chain length, stoichiometry, and concentration on gelation kinetics and other properties are evaluated. Additionally, kinetics of the Diels–Alder reactions in the gelling system are compared with the kinetics of small molecule systems. By combining spectroscopic and rheological techniques, a mechanochemical analysis is performed.
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.
The preparation of a polymer based on Tulipalin A with degradable ester linkages and high glass transition temperature with good processability, and solubility in various organic solvents is reported. The reaction was performed by mixing Tulipalin A and 2‐methylene‐1,3‐dioxepane (MDO) at high temperatures (70 °C and above) in the entire composition range without any initiator. The polymerization mechanism is found to be different from mere thermal initiation at high temperature. It was a combination of ionic and radical mechanism as proved by different methods. Microstructure analysis was done by 1D and 2D NMR techniques. The reactions were also tuned for different structures with varied properties by adding either the radical trapping agent or radical generators in the system.
New degradable, transparent, and elastomeric materials based on PCL are reported in this work. These are block copolymers of PCL with a copolymer of MMA and MDO, i.e. P(MMA‐co‐MDO)‐b‐PCL‐b‐P(MMA‐co‐MDO). A PCL‐based macro‐azoinitiator is used for preparing the block copolymers by free‐radical chemistry. The free‐radical copolymerization of MDO with MMA provides CL units distributed randomly on the PMMA backbone of the second block. This provides the advantage of bringing degradability to the whole system. The detailed structural characterization of the new polymers, their properties evaluation like thermal and mechanical are also reported. The materials are degradable, transparent, and elastomeric depending upon the copolymer composition and block length.
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.
Reductively degradable multiblock polymers for gene and drug delivery were synthesised by oxidative polycondensation of poly(ethylene glycol)‐cysteine derivatives containing ester or urethane bonds. Hydrolysis of the polymers at pH = 5.5, 7.4 and 8.0 and reductive degradation with glutathione and dithiothreitol were studied. The hydrolysis rate of polymer esters increased with increase in pH; the hydrolysis of polymer urethanes was negligible. Chemical substitution of the pendant COOH or NH2 groups significantly affected the rate of the polymer degradation. Surface modification of poly(L ‐lysine)‐DNA complexes with PEG‐cystine multiblocks led to the formation of reductively degradable nanoparticles.
The morphology and thermal stability of bead‐free and uniform electrospun pure polystyrene (PS) and PS/Ni nanocomposite fibers are investigated by SEM and TGA/DSC. A higher thermal stability is observed after introducing the nanoparticles in the polymer fibers. FT‐IR analysis indicates a physical entanglement rather than chemical bonding between the nanoparticles and the polystyrene matrix. The nanoparticles still exhibit superparamagnetic properties even after dispersing in the polymer matrix, different from the reported enhanced coercivity as a result of the enlarged particle distance. However, the magnetic field required to saturate the magnetization is significantly reduced. A further oxidation is deduced after the high voltage electrospinning process.
MWs are explored as the driving force for an SMP based on chemically crosslinked moist PVA networks. The samples show rapid shape recovery under MW irradiation, whereas dry samples experience no shape changes when irradiated. This effect is attributed to the heat created by vibrating water molecules inside the samples that supplies the energy required for shape recovery. The rate of recovery rate is affected not only by the water content in the material but also by the applied MW power output. Automatic network analysis, DSC, and DMA are used to study the dielectric, thermal and mechanical properties of the samples. MW‐induced shape recovery offers advantages such as high and variable recovery rate and the absence of direct contact between the heating source and the material.
Au core/silica shell (Au@SiO2) nanoparticles were synthesized by coating gold NPs with sol/gel silica in alcoholic solution. The alcoholic dispersion was added, in the range of 1–5 wt.‐%, to TPGDA and photocured by means of UV light. Transparent coatings were obtained and they can find suitable applications. It was shown that the NPs can restrict the segmental motion and decrease the free volume of the polymer network, with a consequent increase in glass transition temperature. TEM analysis put in evidence that the particles are well dispersed without any macroscopic agglomeration, and many particles are present as isolated particles.
A series of layer‐structured zinc‐containing metallopolymers were prepared through a solvothermal reaction of zinc acetate with 1,4‐benzene dicarboxylic acid derivatives bearing various nonpolar n‐alkyl groups as side chains. The resulting metallopolymers were investigated. The reaction time and the length of the alkyl substituents on the backbone have a marked effect on the mesophase structure and thermal behaviors of the metallopolymers. The metallopolymer with tetradecyloxy side chains prepared by solid‐to‐solid transformations within solvothermal synthesis exhibits a unique mesophasic behavior with melt tractability.
