Oligo diol

As mentioned previously, the synthesis of polyurethanes, by the reaction of a diisocyanate (or polyisocyanate) with oligo-diols (or oligo-polyols), is a polyaddition reaction (or step-addition polymerisation), a particular type of polycondensation reaction. There is a great difference between the polycondensation and the polyaddition reactions and the classical radical polymerisation or ionic (living) polymerisation reactions. In radical polymerisations (typical chain reactions), the high MW polymer is formed at the beginning of polymerisation. The reaction system is constituted from monomer and high... 

Fig. 10.13. MALDI-TOP spectrum of the model oligo(ethylene terephthalate diol)s. The inset shows an expanded view of the low-intensity peaks in the circle m/z 940-1120). Adapted from Ref. [126] by permission. John Wiley Sons, 1995.

The above description of the process is tentative because it is based on limited data. If it is correct, the predominate structures in the PHBA-modified products have amorphous PA/AA/NPG center sections end-capped with single units or short blocks of oligomeric PHBA. Random distribution of the PHBA cannot be ruled out, but the hetero-geneiety of the products suggests that a substantial fraction of PHBA is incorporated into short blocks. The FT-IR and GPC data are consistent with the proposal that short, phenolic-tipped oligomers are the predominant structure present. The possibility that the materials are physical mixtures of oligo-PHBA and amorphous diols can be virtually ruled out on the basis of the extreme insolubility of oligo-PHBA (IJ) and of the model PHBA-benzoic acid adduct synthesized in this study. These materials separate readily from solutions and dispersions of PHBA copolymers. 

Isosorbide and equimolar amounts of various diols were polycondensed with diphosgene in p3ridine. Different bisphenols, l,3-bis(4-hydroxybenzyloxy)pro-pane, and 1,4-cyclohexane diol were used as comonomers [59]. In some cases, large amounts of cyclic oligo- and polycarbonates were formed. 

This process involves two steps. In the first step, a,co-dihydroxy-terminated oligo(propylene succinate)s (SP) were prepared by the thermal polycondensation of excess diol and diacid, (see first part of Scheme 9). In the second step, the... 

Figure 3.3 General structure of a diol (oligo-polyol with two hydroxyl groups/mol)...

Equation 3.8 for EW is very convenient for practical use because it does not depend on the functionality, which is very difficult to determine. The EW of an oligo-polyol is very useful for the required isocyanate quantity calculation. One equivalent weight of an oligo-polyol reacts with one equivalent weight of the diisocyanate (the MW of the isocyanate divided by the number of -NCO groups). The EW of polyols with the same OH are identical, irrespective of the functionality. Thus a diol with an OH of 56.1 mg KOH/g (MW = 2000) and a triol of the same OH (MW = 3000), have the same EW of 1000. 

The MALDI-TOF spectrum of opportunely synthesized oligo(ethylene terephthalate diol)s (PET-OH) exhibits an intense series of peaks due to sodi-ated linear oligomers with two hydroxyl end-groups. The spectrum also shows... 

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