A Review on Modeling Cure Kinetics and Mechanisms of Photopolymerization.

Photopolymerizations, in which the initiation of a chemical-physical reaction occurs by the exposure of photosensitive monomers to a high-intensity light source, have become a well-accepted technology for manufacturing polymers. Providing significant advantages over thermal-initiated polymerizations, including fast and controllable reaction rates, as well as spatial and temporal control over the formation of material, this technology has found a large variety of industrial applications. The reaction mechanisms and kinetics are quite complex as the system moves quickly from a liquid monomer mixture to a solid polymer.

Dielectric Properties of Shrinkage-Free Poly(2-Oxazoline) Networks from Renewable Resources.

In the course of this study, the dielectric and physicochemical properties of poly(2-oxazoline) (POx) networks from renewable resources were compared with those of fossil-based polyamide 12 (PA 12) networks. POx was synthesized by the energy-efficient, microwave-assisted copolymerization of 2-oxazoline monomers, which were derived from fatty acids of coconut and castor oil. For the preparation of composites, aluminum nitride nanoparticles n-AlN and microparticles μ-AlN as well as hexagonal boron nitride BN submicroparticles were used.

Expanding Monomers as Anti-Shrinkage Additives.

Commonly, volumetric shrinkage occurs during polymerizations due to the shortening of the equilibrium Van der Waals distance of two molecules to the length of a (significantly shorter) covalent bond. This volumetric shrinkage can have severe influence on the materials' properties. One strategy to overcome this volumetric shrinkage is the use of expanding monomers that show volumetric expansion during polymerization reactions.

Temperature-Triggered/Switchable Thermal Conductivity of Epoxy Resins.

The pronouncedly low thermal conductivity of polymers in the range of 0.1-0.2 W m K is a limiting factor for their application as an insulating layer in microelectronics that exhibit continuously higher power-to-volume ratios.

Heat Dissipation in Epoxy/Amine-Based Gradient Composites with Alumina Particles: A Critical Evaluation of Thermal Conductivity Measurements.

For the design of the next generation of microelectronic packages, thermal management is one of the key aspects and must be met by the development of polymers with enhanced thermal conductivity. While all polymer classes show a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers, yielding polymer-based composite materials with high thermal conductivity. The inorganic fillers, however, are often available only in submicron- and micron-scaled dimensions and, consequently, can sediment during the curing reaction of the polymer matrix.

Polyethylene Nanocomposites for Power Cable Insulations.

This review represents a comprehensive study of nanocomposites for power cables insulations based on thermoplastic polymers such as polyethylene congeners like LDPE, HDPE and XLPE, which is complemented by original results. Particular focus lies on the structure-property relationships of nanocomposites and the materials' design with the corresponding electrical properties. The critical factors, which contribute to the degradation or improvement of the electrical performance of such cable insulations, are discussed in detail; in particular, properties such as electrical conductivity, relative permittivity, dielectric losses, partial discharges, space charge, electrical and water tree resistance behavior and electric breakdown of such nanocomposites based on thermoplastic polymers are described and referred to the composites' structures.

Enhancement of the Insulation Properties of Poly(2-oxazoline)-co-Polyester Networks by the Addition of Nanofillers.

Copoly(2-nonyl-2-oxazoline)-stat-poly(2-dec-9'enyl-2-oxazoline)s can be crosslinked by the thiol-ene reaction with glycol dimercaptoacetate. The copoly(2-oxazoline)-stat-copolyester is tested as dielectric for high-voltage applications, either as unfilled resin or as composite with nanoscaled fillers of silica, alumina, and hexagonal boron nitride. During AC voltage tests, all materials have an average breakdown strength of 45-50 kV mm .

Fifty Years of Hydrosilylation in Polymer Science: A Review of Current Trends of Low-Cost Transition-Metal and Metal-Free Catalysts, Non-Thermally Triggered Hydrosilylation Reactions, and Industrial Applications.

Hydrosilylation reactions, the (commonly) anti-Markovnikov additions of silanes to unsaturated bonds present in compounds such as alkenes and alkynes, offer numerous unique and advantageous properties for the preparation of polymeric materials, such as high yields and stereoselectivity. These reactions require to be catalyzed, for which platinum compounds were used in the initial stages. Celebrating the 50th anniversary of hydrosilylations in polymer science and, concomitantly, five decades of continuously growing research, hydrosilylation reactions have advanced to a level that renders them predestined for transfer into commercial products on the large scale.

Effect of Interfacial Polarization and Water Absorption on the Dielectric Properties of Epoxy-Nanocomposites.

Five types of nanofillers, namely, silica, surface-silylated silica, alumina, surface-silylated alumina, and boron nitride, were tested in this study. Nanocomposites composed of an epoxy/amine resin and one of the five types of nanoparticles were tested as dielectrics with a focus on (i) the surface functionalization of the nanoparticles and (ii) the water absorption by the materials. The dispersability of the nanoparticles in the resin correlated with the composition (OH content) of their surfaces.

UV-mediated thiol-ene click reactions for the synthesis of drug-loadable and degradable gels based on copoly(2-oxazoline)s.

An 80-membered library of gels composed of monofunctional 2-ethyl-2-oxazoline and 2-nonyl-2-oxazoline and one of four selected difunctional 2-oxazolines (containing either ether or ester bonds) were synthesized by microwave-assisted ring-opening polymerizations. The difunctional 2-oxazolines were prepared from the thiol-ene reaction of glycol dimercaptoacetate or 2,2'-(ethylenedioxy)diethanethiol and 2-but-3'-enyl-2-oxazoline or 2-dec-9'-enyl-2-oxazoline. 53 of the gels exhibited glass-transition temperatures, which ranged from -5.

Interdisciplinary Approaches towards Materials with Enhanced Properties for Electrical Engineering.

The internationally growing demand for electrical energy is one of the most prominent triggers stimulating research these days.[..

Crosslinked Poly(2-oxazoline)s as "Green" Materials for Electronic Applications.

Poly(2-nonyl-2-oxazoline)--poly(2-dec-9'-enyl-2-oxazoline) and poly(2-dec-9'-enyl-2-oxazoline) can be synthesized from the cationic ring-opening polymerization of monomers that can be derived from fatty acids from renewable resources. These (co)poly(2-oxazoline)s can be crosslinked with di- and trifunctional mercapto compounds using the UV-induced thiol-ene reaction. The complex permittivity of the corresponding networks increases with the temperature and decreases with the network density.

Modification Pathways for Copoly(2-oxazoline)s Enabling Their Application as Antireflective Coatings in Photolithography.

Chromophore-functionalized copoly(2-oxazoline)s are successfully evaluated as bottom antireflective coatings (BARCs) in high-resolution photolithography. With respect to UV light sources used in photolithographic production routines, anthracene is chosen as a chromophore. For application as polymer in BARCs, the copolymer poly(2-ethyl-2-oxazolin)45 -stat-poly(2-dec-9'-enyl-2-oxazolin)20 -stat-poly(2-(3'-(1"-(anthracen-9-ylmethyl)-1",2",3"-triazol-4-yl)propyl)-2-oxazolin)35 can be synthesized by the Huisgen cycloaddition click reaction of the copolymer poly(2-ethyl-2-oxazolin)45 -stat-poly(2-dec-9'-enyl-2-oxazolin)20 -stat-poly(2-pent-4'-inyl-2-oxazolin)35 and the corresponding azide-functionalized anthracenes.

Microwave-assisted cationic ring-opening polymerization of 2-oxazolines.

Unlike any other polymer class, the (co-)poly(2-oxazoline)s have tremendously benefited from the introduction of microwave reactors into chemical laboratories. This review focuses on the research activities in the area of (co-)poly(2-oxazoline)s prepared by microwave-assisted syntheses and, correspondingly, summarizes the current-state-of the-art of the microwave-assisted synthesis of 2-oxazoline monomers and the microwave-assisted ring-opening (co-)polymerization of 2-oxazolines as well as prominent examples of post-polymerization modification of (co-)poly(2-oxazoline)s. Special attention is attributed to the kinetic analysis of the microwave-assisted polymerization of 2-oxazolines and the discussion of non-thermal microwave effects.

Microwave-Assisted Syntheses in Recyclable Ionic Liquids: Photoresists Based on Renewable Resources.

The copoly(2-oxazoline) pNonOx80 -stat-pDc(=) Ox20 can be synthesized from the cationic ring-opening copolymerization of 2-nonyl-2-oxazoline NonOx and 2-dec-9'-enyl-2-oxazoline Dc(=) Ox in the ionic liquid n-hexyl methylimidazolium tetrafluoroborate under microwave irradiation in 250 g/batch quantities. The polymer precipitates upon cooling, enabling easy recovery of the polymer and the ionic liquid. Both monomers can be obtained from fatty acids from renewable resources.

The π-Electron Delocalization in 2-Oxazolines Revisited: Quantification and Comparison with Its Analogue in Esters.

The single crystal X-ray analysis of the ester-functionalized 2-oxazoline, methyl 3-(4,5-dihydrooxazol-2-yl)propanoate, revealed π-electron delocalization along the N-C-O segment in the 2-oxazoline pentacycle to significant extent, which is comparable to its counterpart along the O-C-O segment in the ester. Quantum chemical calculations based on the experimental X-ray geometry of the molecule supported the conjecture that the N-C-O segment has a delocalized electronic structure similar to an ester group. The calculated bond orders were 1.

Poly(2-oxazoline)-derived contact biocides: contributions to the understanding of antimicrobial activity.

A set of poly(2-oxazoline)-derived (co-)polymers was prepared by microwave-assisted polymerizations and acid-mediated hydrolysis and tested for antimicrobial activity in 50 × 50 × 2 mm PP compound plates containing 5 wt% of the polymers. Antimicrobial activity against gram-negative E. coli and P.

Strategies for the synthesis of poly(2-oxazoline)-based hydrogels.

Poly(2-oxazoline)-based networks currently receive great interest due to their versatile properties that can be tailor made by desktop-planned modifications. This feature summarizes strategies for the preparation of these networks, comprising the in situ cross-linking as well as polymer-analogous cross-linking routines such as (reversible) complex formation, physical processes, and covalent bond formation (involving reactions with olefinic species as well as with epoxides, isocyanates, aldehydes, acids, and their derivatives). Reflecting prominent application examples in the biomedic(in)al sector, poly(2-oxazoline)-co-polyester networks are described in a dedicated section.

Water-developable poly(2-oxazoline)-based negative photoresists.

Copoly(2-oxazoline)-based photoresists are prepared from pEtOx(80) Bu(=) Ox(20) and pPhOx(80) Dc(=) Ox(20) , respectively, a tetrathiol, and a photosensitive initiator. It is possible to prepare copoly(2-oxazoline)s bearing unsaturated side chains in a microwave reactor on a decagram scale in reaction times of 100 min or shorter. UV irradiation of dried polymer films through a quartz mask induces the thiol-ene reaction in the illuminated areas.

Synthesis of poly(2-oxazoline)-based hydrogels with tailor-made swelling degrees capable of stimuli-triggered compound release.

A 32-membered library of poly(2-oxazoline)-based hydrogels of the composition pEtOx(m) -pPhOx(n) -pPBO(q) (m/n = 150/0, 100/50, 50/100, and 0/150; q = 1.5-30) was prepared from 2-ethyl- (EtOx), 2-phenyl-2-oxazoline (PhOx), and phenylene-1,3-bis-(2-oxazoline) (PBO). The polymerizations were performed from ground monomer mixtures at 140 °C in a single-mode microwave reactor in reaction times as short as 1 h.

Anhydrous thallium hydrogen L-glutamate: polymer networks formed by sandwich layers of oxygen-coordinated thallium ions cores shielded by hydrogen L-glutamate counterions.

Anhydrous thallium hydrogen L-glutamate [Tl(L-GluH)] crystallizes from water (space group P2(1)) with a layer structure in which the thallium ions are penta- and hexacoordinated exclusively by the oxygen atoms of the γ-carboxylate group of the hydrogen L-glutamate anions to form a two-dimensional coordination polymer. The thallium-oxygen layer is composed of Tl(2)O(2) and TlCO(2) quadrangles and is only 3 Å high. Only one hemisphere of the thallium ions participates in coordination, indicative of the presence of the 6s(2) lone pair of electrons.

One decade of microwave-assisted polymerizations: quo vadis?

The application of microwave irradiation in polymer syntheses and modifications is of continuously growing interest and has received significant international interest since the beginning of the millennium. Preceded by a review that was published 6 years ago, the present paper summarizes the most recent trends in this research area. Radical as well as step-growth and ring-opening polymerizations will be addressed; furthermore, the evolution from microwave-assisted polymerizations to microwave-assisted material fabrication will be described on the examples of polymeranalogous reactions, polymer/metal composites and bio-based materials.

Evaporation induced micellization of poly(2-oxazoline) multiblock copolymers on surfaces.

The formation of micelles on surfaces by spin-coating dilute solutions of diblock, triblock, and tetrablock copoly(2-oxazoline)s in a non-selective solvent is demonstrated. The micelles are not preexistent in the initial solution but are formed during the evaporation of the solvent by precipitation of the least-soluble block. The morphology and size of the micelles vary according to the fraction of this block but are not dependent on the block order in the copolymer.

Interactions of a beta-dipeptide with monovalent metal cations: crystal structures of (anthranoyl)anthranilic acid and its lithium, sodium and thallium salts.

X-ray crystal structure analyses have been performed on the beta-dipeptide (anthranoyl)anthranilic acid [HAnthAnthOH] and its lithium, sodium and thallium salts [HAnthAnthOM] to give a first set of data for this representative model ligand. Crystals of the beta-dipeptide are orthorhombic, space group Pca2(1). The unit cell contains two molecules of (anthranoyl)anthranilic acid which form a dimer via hydrogen bonds.