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.
Star polymers with methacryloyl groups at the chain ends were synthesized by esterification of hydroxyl end‐functional star polymers. First, the linear hetero‐telechelic macroinitiator (MI) was prepared by ATRP using a functional initiator. The obtained MI was chain‐extended and cross‐linked with DVB and then esterified into methacryloyl chain‐end functionality. The degree of esterification was controlled by changing the initial molar ratios of methacryloyl chloride to hydroxyl groups. The methacryloyl‐containing star polymers were cross‐linked either intermolecularly or intramolecularly under heating or UV irradiations, depending on the concentrations of star polymers during the cross‐linking reactions.
A supramolecular polymer gel is formed by host‐guest interactions between a DB24C8‐based bis(crown ether) and a copolymer containing the dibenzylammonium moiety. The formation of the gel and its cross‐linked networks structure are evidenced by 1H NMR spectroscopy, viscometry, and SEM. Interestingly, the gel shows both pH‐ and thermoesponsive behaviors, and excellent self‐healing properties. The self‐healing property of the gel is tested by rheological measurements, and it can also be seen visually and directly. The presented work provides a new strategy for the construction of the self‐healing supramolecular polymer gels with potential applications in smart materials.
A new technology to measure the kinetics of bulk radical polymerization is presented. This technology is easy to connect with all systems using irradiation light, including Raman and IR measurement setups. The curing kinetics of commercially available offset printing dyes (acrylic esters) with initiators have been studied in situ in real‐time by light transmission. The setup consists of a slightly modified diode array UV–Vis spectrometer with a dual purpose xenon arc flash lamp light source. The lateral dependency (irradiation dosage) of the change in the transmitted light has the potential to be interesting for scientific and industrial applications. In addition, options for kinetics studies and quantum efficiencies are introduced to expand the possibilities of studying the polymerization processes.
Living free‐radical copolymerization of the inimer 4‐vinylbenzyl N,N‐diethyldithiocarbamate with maleic anhydride in the presence of methyl methacrylate produces highly branched poly(methyl methacrylate) star polymers. Subsequently, mikto‐arm stars can be synthesized by condensation of poly(ethylene glycol methyl ether) monosodium alkoxide with functional maleic anhydride sites in the hyperbranched core. The solution properties of these mikto‐arm star copolymers are discussed.
A novel time‐ and cost‐saving technique to fabricate a CNT composite film was suggested by using poly(acrylonitrile) nanoparticles coated with functionalized carbon nanotubes. Composite films were formed with fCNTs attached to nanoparticles by hot pressing onto PMMA films. The electrical properties (conductivity and electromagnetic interference shielding effectiveness) of the films were investigated. It was observed that CNT/polymer composite films with PAN nanoparticles coated with fCNTs showed good electrical properties because of enhanced dispersity of CNTs in the polymer matrix.
The step‐growth polymerization of glycerol to relatively high molecular weight polyglycerol is investigated. Glycerol is a renewable material that can be derived from the transesterification of vegetable oils to biodiesel. Several soluble catalysts and their reaction mechanisms are compared and their effect on polymer molecular weight and microstructure is measured. High‐molecular‐weight PG with multimodal molecular weight distributions is observed using GPC, and partial branching is identified using 13C NMR spectroscopy. Theoretical models are used to predict the gel point and to calculate monomer functionality.
The molar mass distributions of high‐molar‐mass PE and PP were characterized using HT‐AF4 and HT‐SEC in combination with IR and MALS detection. Calculated molar mass distributions, average molar masses and radii of gyration were compared. It was found that HT‐AF4 can detect the real extent of thermo‐oxidative degradation during dissolution. HT‐SEC is affected by shear and thermo‐oxidative degradation while in HT‐AF4 no shear stress exists. As a consequence, the molar mass averages obtained from HT‐SEC are pronouncedly lower as obtained from HT‐AF4. In addition, branched polyolefins cannot be correctly characterized by SEC‐MALS due to abnormal co‐elution effects. HT‐AF4 is therefore the method of choice for studying the thermo‐oxidative degradation of macromolecules with high molar masses.
Three 2,5‐substituted polar PPV derivatives have been prepared using the sulfinyl precursor route and compared to the apolar MDMO‐PPV. All polymers were obtained in excellent yield and with improved purity as compared to other methods. The influence of the polarity of the side chains, i.e. oligo(oxyethylene) and alkyl substituents, on the optical and electronic properties were investigated. In thin films, the oligo(oxyethylene) substituents do not significantly alter the optical properties of the conjugated backbone and the field effect mobility. In contrast, other thin film electrical properties, such as relative permittivity and conductivity, are markedly affected by the polar substituents. This is also the case for their solubility and solution properties. The polar PPV‐derivatives are not only soluble in a wide range of solvents, but also exhibit aggregation phenomena.
The nanocomposites of liquid‐crystal polymer (LCP) with two different weight per cents of clay were prepared via the melt extrusion method. To investigate the properties of the materials in the linear and non‐linear viscoelastic regions, both oscillatory and rotational tests were carried out. The results showed that the nanocomposite with higher clay content exhibited an almost defectless partially cross‐linked structure compared to the nanocomposite with lower clay content or the pure LCP. The linear stress relaxation measurements revealed that the pure LCP relaxed faster than nanocomposites after imposition of a constant strain for a specific time. During the step rate relaxation test, high shear rate modified the defects in the pure LCP very quickly and probably attained almost an equilibrium position while the nanocomposite samples showed strong shear thinning behaviour.
The bis(acetylacetonato)platinum(II) is a common thermal catalyst for the hydrosilation reaction, and it is reported to serve also as a photoactivated catalyst for hydrosilation addition of silanes to alkenes and alkynes. In this paper, it is demonstrated that the UV‐activation of hydrosilation reaction proceeds via a thermal‐frontal mechanism. UV light activates the polymerization on the surface of the sample and, subsequently, the heat released by hydrosilation generates a thermal front, converting the UV‐generated homogeneous catalyst to a Pt0 heterogeneous catalyst. The UV‐induced frontal polymerization mechanism can exhaustively explain the dark‐curing process observed in the UV‐activated hydrosilation reaction.
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 one‐step synthesis of heterobifunctional hyperbranched polyethylenes covalently tethered with dual acryloyl and 2‐bromoisobutyryl functionalities at controllable contents is reported. It is achieved in one pot by chain‐walking terpolymerization of ethylene with two functional acrylate comonomers, 1,6‐hexanediol diacrylate and 2‐(2‐bromoisobutyryloxy) ethyl acrylate. The unique chain‐walking mechanism renders the hyperbranched polymer chain topology and its remarkable capability in incorporating acrylate comonomers enables the incorporation of both comonomers to give two valuable functionalities. The two comonomers exhibit nearly equal vinyl reactivity and are incorporated independently in the terpolymerization with their molar contents controlled by adjusting the comonomer feed concentrations.
Mixtures of DGEBA with 4‐phenyl‐γ‐butyrolactone (PhBL) were cationically copolymerized in the presence of ytterbium triflate or triarylsulfonium hexafluoroantimoniate as thermal or photo initiator respectively. Changes during curing and final properties of the cured materials were studied by means of DSC, FT‐IR/ATR, TMA, DMTA, TGA and densitometric measurements. The formation of a network containing polyether and poly(ether‐ester) moieties was demonstrated to take place through the ring‐opening polymerization of a spiroorthoester intermediate (SOE) formed during the copolymerization. An increase in the proportion of lactone resulted in an increase in the curing rate, a decrease in the shrinkage after gelation and in the thermal stability and glass transition temperature (Tg). A strong influence of the initiator on the curing mechanism was observed. As a consequence, the photocured materials exhibited superior thermal stability and Tg than those obtained thermally.
εCL was polymerized using the triflates of lanthanum, samarium, magnesium, aluminum, scandium, and bismuth as catalysts. Bismuth triflate proved to be extraordinarily reactive, and catalyzed polymerizations of εCL even at 20 °C. Adding DTBMP reduced the polymerization rate only slightly. Furthermore, no evidence of a cationic mechanism was found by end‐group analyses. Polymerization at 20 °C either in bulk or in solution only yielded polyesters of low or medium molecular weights ($\overline {M} _{{\rm n}} $ up to 30 000 Da). Yet addition of alcohols allowed for a proper control of molecular weight and end‐groups. Additionally, low catalyst concentrations and low temperature resulted in narrow molecular weight distributions and polylactones almost free of cyclic compounds.
The Ni‐catalyzed polymerization of P3AOTs was studied and compared with the controlled chain‐growth polymerization of P3ATs. By varying the ratio of the initial monomer concentration to the initiator concentration, no linear dependence of the molar mass was observed, revealing that the polymerization does not proceed via a controlled mechanism. This was also confirmed by analyzing the end‐groups of the polymer with MALDI‐TOF mass spectrometry. To acquire more information on the polymerization mechanism, the formation of the actual monomer and the polymerization reaction were studied into more detail. These experiments proved that the polymerization proceeds via a chain‐growth mechanism, although not in a controlled way.
Combinatorial and high‐throughput experimentation is used to accelerate the rate of experimentation in macromolecular science. Combinatorial and high‐throughput methods are used in macromolecular science to discover and optimize catalysts for polymerization reactions, discover compositions that have specific desired properties, and systematically explore polymer structure–property relationships. The use of high‐throughput methods can enable the discovery of complex catalyst systems or polymer compositions that would not be feasible using conventional experimental methods. In addition, combinatorial data can be used as inputs into computer models to enable the accurate prediction of material properties as a function of composition.
A new 1,2,3‐triazole incorporated diacrylate monomer is designed for free radical cyclopolymerization through the formation of 11‐membered rings. NMR analysis on the cyclopolymers including 1H, 13C, DEPT‐135, and 1H–13C HMQC spectra support a high degree of cyclization. GPC profiles of the obtained cyclopolymers show unimodal distributions indicative of no chain branching reactions.
Tunable alkaline anion‐exchange membranes based on QPMBV are synthesized using a bottom‐up approach, miniemulsion copolymerization, which can incorporate functional groups into the copolymers with designated composition and high molecular weight. The mechanical and electrochemical properties of the obtained QPMBV membranes are tuned by varying the composition. It is found that the ion exchange capacity of the copolymer, the hydrophilicity of the copolymer chains, the molecular weight, and the glass transition temperature of the copolymers are essential to balance the mechanical and OH– transport properties of QPMBV membranes. QPMBV membrane fuel cells show the best power output and the long‐lasting fuel cell performance among the APE membranes in open literature.
