Solution properties, oligomers

Fluorene oligomers, especially those functionalized at the C-9 position, are readily soluble in common organic solvents. The most striking example is in a study of a series of oligofluorenes static and dynamic solution properties, where they remain soluble at concentrations greater than 500 g L-1 in toluene, or > 50 wt. %, and even up to 800 g L-1 in the case of a terfluorene [ 120]. Routinely, fluorene oligomers are purified in solvent mixtures consisting mostly of nonpolar hexanes, and then solution-cast into thin films. 

What is the minimum degree of polymerization necessary for dextran to exhibit properties characteristic of a typical polymer This question should be resolved by examining the molecular weight dependence of its solution properties, although this may be subject to the limitation that native dextran is not a linear polymer but a branched one. The optical rotation data in Figure 2 demonstrate the transition from oligomer to polymer aroxmd the... 

My new theory is applicable to mixtures of small molecules, as well as to polymer solutions. Using extremely precise experimental data from the literature, I find excellent agreement, checking the basic assumptions of my theory. With these checks, I am now refining my theory for polymer solutions, dealing especially with the temperature and concentration dependence, relations of the parameters to molecular compositions, and the prediction of parameters from data on the pure components and other related systems. A new treatment of the thermodynamic properties of solutions of oligomers is being prepared for publication. 

Amine-terminated siloxane oligomers have also been utilized in the synthesis of various siloxane-amide and siloxane-imide copolymers, High molecular weight siloxane-amide copolymers have been synthesized by the solution or interfacial co-polymerization of siloxane oligomers with sebacoyl chloride or terephthaloyl chloride respectively 1S5,165). In some reactions diamine chain extenders have also been utilized. Thermal and dynamic mechanical characterization of these copolymers have shown the formation of multiphase systems160). Compression molded films displayed very good elastomeric properties. 

Dendrimers have distinctive properties, such as the ability to entrap small molecules in their core region and very low intrinsic viscosities in solution. Such properties require molecules to have achieved a particular size, and not all molecules with branches radiating from a core are large enough to develop the characteristic properties of true dendrimers. Branched molecules below this critical size are called dendrons and are the equivalent in dendrimer chemistry of oligomers in polymer chemistry. 

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