Oligomers cross-linkers

Fig. 10. Generalized formulation design outline for radiation-curable coatings and adhesive systems. The cross-linker is a multifimctional unsaturated cross-linking agent or oligomer, rj = viscosity CR = cure rate S = shrinl ge H = hardness F = flexibility A = adhesion 7 = surface energy ...

Several polymer-related uses of brassylic acid (BA) have been investigated. For example, a BA/l,3-butanediol/lauric acid oligomer is an effective plasticizer for poljrvinyl chloride,[6] BA/ethylene glycol and BA/propylene glycol polymers function as polyester based polyurethane elastomers,[7] and BA has been patented as a cross-linker for glycidyl methacrylate copolymer powder coatings.[8] However, the most detailed studies have involved polyamides selected data from these studies are summarized in Table I. 

A number of hetero-bifunctional cross-linkers have been developed for covalent attachment of thiol-modified DNA oligomers to aminosilane mono-... 

Otherwise a co-network would have been obtained. Thus PDMS network was formed starting from a,co-(3-hydroxypropyl)polydimethylsiloxane (diOH-PDMS oligomer) by DBTDL catalyzed addition between the hydroxy end groups and an pluri-isocyanate cross-linker (Scheme 2). No side reaction has been detected between these precursors. 

Chain Extenders and Cross-linkers. In addition to the two principal components of most urethane coatings, isocyanate and polyol components, a number of di- or polyfunctional, active hydrogen components may be used as chain extenders or cross-linkers. The most important classes of compounds for this use are diols or polyols (monomers or oligomers), diamines, and alkanolamines. Typical examples of diols are ethylene, dlethylene, dlpropylene glycol, 1,4-butanedio1, 1,5-hexanediol, neopentyl glycol,... 

Section 2.4 describes cross-linkers and their handling. Figures 8.5 and 8.6 show how simple the determination of the subunit composition of an oligomer theoretically is with cross-linkers. A detection assay is required for the oligomer, for the purified oligomer, and for specific antibodies against the subunits. 

First, the experimenter estimates the MW of the oligomer (hydrodynamic measurements, radiation inactivation) and the MW of the subunits (SDS gel electrophoresis of the purified oligomer). She then treats the oligomer with cross-linkers (e.g., from the bismuthate family)... 

High concentrations of cross-linkers or protein lead to intermolecular cross-linking, or the oligomer in solution partially aggregates to high-molecular complexes. Both lead to an overestimated number of subunits. 

Cross-linking of the oligomer s monomers is not continuous but stepwise with increasing concentration of cross-linker. The intermediate steps dimer, trimer, and so on do not occur then. On the SDS gel, you only see the monomers and/or high-molecular adducts. 

The quantitative analysis of cross-linking data yields evidence about the structure of the homooligomer. The homooligomer is incubated with different concentrations of cross-linker, the reactions are stopped after a certain time, and the solutions are separated on an SDS gel. Monomers, cross-linked dimers, and so on appear in the gel. The relative amount of monomers and cross-linked oligomers is determined for each cross-linker concentration (e.g., by scanning the gel). From the amounts, the cross-linking probabilities between the single subunits are computed (and from this the structure). 

Norbornenyl functionalised linseed oil and cyclopentadiene oligomer-based thermosetting resins have been successfully synthesised using dicy-clopentadiene or other polycyclic norbornene-based comonomers as cross-linkers. New biorenewable-based thermosets have been successfully synthesised by the ring opening metathesis polymerisation of norbornenyl functionalised fatty alcohols of soybean and castor oils. The castor oil-based thermoset exhibits lower soluble fractions and higher thermal stability and mechanical properties compared with the soybean oil-based thermoset. This is due to more effective cross-linking. ... 

Silicone RTV sealants are HO-Silicone-OH oligomers + CH3S1X3 cross-linkers, where X is -OCH3, -O2CCH3, or-N=C(CH3)2. 

Chrisey, Lee, and O Ferrall describe an interesting use of sulfhydryl-mediated immobilization for binding thiol-modified DNA. A hetero-bifunctional cross-linker bearing both thiol and amino reactive groups was used to immobiUze thiol-modified DNA oligomers to self-assembled monolayer silane films on fused silica and oxidized silicon substrates. The advantage of this approach... 

Most industrial chemicals and polymers are not the 100% pure, single chemicals as described in their general chemical stmctures. In the case of epoxy resins, they often contain isomers, oligomers, and other minor constituents. As a first requirement, one would need to know the epoxy content or EEW of the epoxy resin so the proper stoichiometric amoimt of cross-linker(s) can he calculated. However, a successful thermoset formulation must also have the proper reactivity, flow, and performance. Consequently, other epoxy resin properties are required by the formulators and supplied by the resin producers. 

Growth of particles After the rapid nucleation period, the polymerization of residual monomer may take place at various domains (i.e., water phase, on the surface of the formed particle, and in the swelled parts of the particles). In fact, the partition of the monomer between the water phase and polymer particles should be considered (1) polymerization in the water phase leads to the formation of small oligomers that can be cross-linked on the formed particles when there is a sufficient residual cross-linker agent concentration,... 

Another approach is based on multi-component systems [97-101]. It has been pursued, in particular, by the group of Professor Dalton. In many cases they have used a two components system formed by a polyurethane NLO oligomer with isocyanate end groups that is reacted with a cross-linking agent, triethanolamine, as example [102, 103]. In this approach, the oligomer (or prepolymer) is prepared first then a solution of the oligomer and of the cross-linker is spin-coated on the substrate (Fig. 2.25). 

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