Oligomer-based approaches

Table 2 gives properties of compositions based on modified resin. As seen from these data, with respect to water- and heat-resistance, as well as the electric resistance after boiling in water the compositions based on the modified resin are superior to those based on the carbamide-formaldehyde oligomer and approach materials based on the melamine-formaldehyde oligomer. 

Later the same polymerization technique proved to be successful in the preparation of multiblock copolymers from poly(oxyethylene)dicarboxylic acid and a polyamide oligomer based on bis(4-aminophenyl)ether and isophthalic acid. The synthesis could be carried out either by a one-pot two-step method [52] or using a two-pot technique by first isolating the polyamide oligomer [11]. The two approaches lead to copolymers with similar thermal and mechanical properties, though this was not the case when a one-pot, one-step method was used [52], probably because of the formation of a more irregular structure. 

Layer-by-layer Ru3 cluster-based multilayers were fabricated onto preorganized self-assembled monolayer gold electrode surfaces by Abe et al. [15], in which [Ru3(q3-0)( i-0Ac)6(4,4/-bpy)2(C0)] was utilized as the synthetic precursor. The stepwise connection of oxo-centered triruthenium cluster units onto the gold electrode surface is a feasible approach for construction of Ru3 cluster-based oligomers on a solid surface, in which the bridging ligand 4,4 -bipyridine appears to mediate weak cluster-cluster electronic interaction between the Ru3 cluster centers. 

A wide variety of new approaches to the problem of product separation in homogeneous catalysis has been discussed in the preceding chapters. Few of the new approaches has so far been commercialised, with the exceptions of a the use of aqueous biphasic systems for propene hydroformylation (Chapter 5) and the use of a phosphonium based ionic liquid for the Lewis acid catalysed isomerisation of butadiene monoxide to dihydrofuran (see Equation 9.1). This process has been operated by Eastman for the last 8 years without any loss or replenishment of ionic liquid [1], It has the advantage that the product is sufficiently volatile to be distilled from the reactor at the reaction temperature so the process can be run continuously with built in product catalyst separation. Production of lower volatility products by such a process would be more problematic. A side reaction leads to the conversion of butadiene oxide to high molecular weight oligomers. The ionic liquid has been designed to facilitate their separation from the catalyst (see Section 9.7)... 

Figure 4. (Phenylene ethynylene)-based conjugated oligomers prepared in solution using a bi-direction growth approach with in situ deprotection and coupling.

Another approach was attempted by Seppala and Kylma who reported the synthesis of poly(ester-urethane)s by condensation of hydroxyl terminated tel-echelic poly(CL-co-LA) oligomers with 1,6-hexamethylene diisocyanate (Scheme 33) [94]. The diisocyanate acts as chain extender producing an increase in molecular weight of the preformed oligomers. The authors claim that some of the copolymers present elastomeric properties. Using a similar method. Storey described the synthesis of polyurethane networks based on D,L-LA, GA, eCL,... 

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