Segment length distributions

Miller J.A., Lin S.B., Hwang K.K.S., Wu K.S., Gibson P.E., and Cooper S.L. Properties of polyether-polyurethane block copolymers Effect of hard segment length distribution. Macromolecules, 18, 32, 1985. 

From experimental data we would like to visualize the segment length distributions - in order both to gain some imagination of the type71 of the distribution - and in order to understand the arrangement of the domains in the material. This visualization is achieved by computation of... 

In conclusion it can be stated that, based on the already positive results and new findings discussed above, photochromic molecules can be used as probes for the study of some of the open questions in the area of polyurethanes mentioned at the beginning this technique will further be employed in future work with photo-chromic polyurethane elastomers of known segment length distributions. 

Miller J, et al. Properties of polyether-polyurethane block copolymers effects of hard segment length distribution. Macromolecules 1985 18 32 4. 

In -this paper, we will shortly discuss our approach to prepare hydroxy-terminated MDl/BDO-based urethane oligomers and their 4-diphenylmethane carbamates, 18 and describe in more detail the synthesis of monodisperse hydroxy-terminated oligo(oxy-tetramethylenes), their use for the investigation of the prepolymer formation, and the synthesis of linear PU-elastomers with narrow (monodisperse) soft and/or hard segment length distribution by using the hydroxy-terminated segment precursors. The chemical structures of the model systems studied in this... 

Fig. 9. Reaction scheme for the synthesis of PU elastomers with strictly monodisperse hard segments and narrow soft segment length distribution made with hydroxy-terminated polyurethanes Diol-n and polyethers POTM-n (see Figure 3) ... 

A widely held opinion is that the segment length distribution in the two-step process follows the most probable form no matter what the reaction conditions of the polyaddition are. However, this is only reasonable to be assumed if the reaction is carried out in solution, and there are indications in the literature that more or less pronounced deviations have... 

Fig. 21. GPC trace of the segmented PU elastomer PU-4 with monodisperse hard segment length distribution (cf, reaction scheme Fig. 10) before (—) and after heating in DMA solution (1 weight % PU-4) at 75 C in the presence of dibutyltin dilaurate catalyst (0.15 weight %) for 2 hr ( ) and 4 or 6 hr ((------------)/ identical chromatograms).

Fig. 23. Dynamic mechanical properties of the segmented PU elastomer PU-4 with monodisperse (n=3, cf. formula in Fig. 3 (—)) and PU-4 with poly-disperse hard segment length distribution (POTM-28/MDI/BDO=1 4 3).

Fig. 24, Dynamic mechanical properties of segmented PU elastomers PU-h with polydisperse hard segment length distribution (POTM-28/MDI/BDO=1 n (n-1) n varying from 2 (PU- ) to 7 (PU-7)).

Fig. 25. Dynamic mechanical properties of segmented PU elastomers PU-n with POTM-TF soft segment and strictly monodisperse hard segment length distribution n varying from 1 (PU-2) to 5 (PU-6). 

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