Siloxane-type polymers flexibility

Polymers derived from the preceding type of reaction with nitriles,5 amines,6 and phosphines,7 have been reported. Green8 has reported the preparation of a resin-type material composed of at least 10 repeat units from the reaction between decaborane and adiponitrile (NC(CH2)4CN). Also reported,9 is the inclusion of flexible siloxanes and ether linkages into a diamine, and of their subsequent reaction with decaborane to give adduct polymers (see 2, 3). 

The type of carbosilane core and the length of siloxane arms play an important role in this process. For high siloxane arms the more flexible core (B) causes large (AH = 14 J/g for B-R-4 versus AH =34 J/g for R-4), but slightly less pronounced decrease of transition enthalpy than compact ones [A, C (AH =4J/g for C-R-4)] (Fig. 5). It implies easier orientation of polymer chains on heating. The opposite was found for lower polymers (AH =3 J/g for B-R-2 and AH =8 J/g for C-R-2). 

Recently we have been seeking new types of organosilicon polymers with the hope of finding polymers having unique structures and interesting combinations of properties. Out of this work has come a new siloxane that is, at least in part, inherently fibrous. The fibers characteristic of it have very small diameters and are flexible and inert. 

Silicone polyethers are non-ionic in nature, and have both a hydrophilic part (low molecular weight polymer of ethylene oxide or propylene oxide or both) and a hydrophobic part (the methylated siloxane moiety). The polyether groups are either ethylene oxide or propylene oxide, and are attached to a side chain of the siloxane backbone through a hydrosilylation or condensation process. They can form a rake-like, comb structure, or linear structure. Silicone polyethers are stable up to 160-180 degrees Celsius. There is a great degree of flexibility in designing these types of polymers. A very wide variety of co-polymers is possible when the two chemistries are combined. 

Silarylene Polymers. Silarylene polymers can be best described as those polymers which contain silicon atoms and phenyl units in the polymer backbone. Perhaps the best example, and the one which has been given the most scrutiny, is poly(tetramethyl-p-silphenylenesiloxane), Q). The major reason which has been cited for incorporating arylene units into this type of polymer has been to increase the thermal stability of the material while maintaining the low temperature flexibility which is associated with siloxane polymers.3.4,5... 

T is a constant depending upon the type of polymers, solvent and temperature. The slope, a, of the log[/j] vs. log Mn plot depends on the type of polymer a = 0 for spheric particles, a = 0.5-1.0 for flexible linear polymers and a = 1.0-2.0 for rigid rod-like polymers. As indicated in Figure 12-17, a is 0.75 for the solution with r = 1 and 0.64 for the solution with r = 2, meaning that these two solutions contain flexible linear siloxane polymers. On the other hand, a ranges from 0.2 to 0.5 for the other two solutions with r = 5 and 20. This means these two solutions contain spherically grown particles. Actually, however, those conclusions have to be checked by other techniques, in addition to viscosity measurements. 

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