Polybutadienes hydroxyl groups

The terminal hydroxyl groups in hydroxy-telechelic polybutadiene are assumed to be predominantly primary alcohols linked to c/s-1,4, trans-1,4, and 1,2 butadiene units [72], Detailed structure of the butadiene or isoprene units at both terminals was studied by the use of 2H-NMR [73], as shown in Section 6.1... 

It is also possible to synthesize hydroxytelechelic polymers with non-hydroxylated azo compounds the a, difunctional polymers were prepared first and the reactive terminal ends were transformed into hydroxyl groups. For example, hydroxytelechelic polybutadienes were synthesized 9,36) by reduction with lithium aluminium hydride of ester-terminated polybutadienes which were obtained by polymerization in the presence of diethyl-2,2 -azobisisobutyrate. 

One observes that the majority microstructure is 1,4 trans. The terminal hydroxyl groups are exclusively primary hydroxyl groups of the allylic type (95%). The functionality (f) of these polybutadiene polyols is in the range of 2.2 - 2.6 OH groups/mol. 

The transformation of the anionic chain end in hydroxyl groups is made by the reaction of living anionic polybutadiene with propylene oxide or ethylene oxide, followed by hydrolysis or by neutralisation of the resulting alcoholate groups (reactions 9.10 and 9.11) [21-24]. 

In Chapter 3, the chemistry and technology of the most important oligo-polyols used for elastic polyurethanes fabrication, in fact high MW oligomers (2000-12000 daltons) with terminal hydroxyl groups and low functionality (2-4 hydroxyl groups/mol) were discussed. Polyalkylene oxide polyols (homopolymers of PO or copolymers PO - EO, random or block copolymers), polytetrahydrofuran polyols, filled polyols (graft poly ether polyols, poly Harnstoff dispersion - polyurea dispersions (PHD) and polyisocyanate poly addition (PIPA) polyols), polybutadiene polyols and polysiloxane polyols were all discussed. The elastic polyurethanes represent around 72% of the total polyurethanes produced worldwide. 

Hydroxyl-Terminated Hydrocarbon Polymers. Although low molecular weight hydroxyl-terminated polybutadienes have previously been reported (lOl). homopolymers and copolymers of butadiene having terminal hydroxyl groups have been commercially available (102). The homopolymers have a molecular weight range of 2500-3500 and the hydroxyl functionality varies from 2.1 to 2.6. 

Kim and Chung point out the qualitative difference between pure polybutadiene, which does not form a monolayer on the water surface, and polybutadienes with hydroxyl side groups. This contribution mainly focuses on polymers with a large number of hydroxyl groups per chain. The lowest number of hydrophilic groups is on average one hydroxyl group in every ten repeat units and the authors discuss the system in the context of polymers with surface active repeat units [13]. 

Ethylene polymerized with diethyl peroxydicarbonate contains terminal ester groups (41). Using C-labeled cyclohexane peroxydicarbonate, the fate of the primary radicals during the polymerization of methyl methacrylate (MMA) and styrene has been studied (42). Although this reference includes no detailed analysis of the products, it indicates that ROOCO-terminated polystyrene telechelics may be obtained by this technique. A similar method has been used for the preparation of telechelic polybutadiene (43). The carbonate end groups are easily modified into terminal hydroxyl groups by hydrolysis. Hydrogenation of the carbonate functionahzed telechelic polybutadiene, followed by hydrolysis, srields hydroxy-terminated polyethylene telechelics. 

This simple and rapid HPLC analysis provides direct proof of the structure of the polymers. The classical approach which compares measured Mn to measured hydroxyl equivalent shows only that on average there is one hydroxyl group per molecule. Chromatography has been used to do similar analyses of hydrocarbon polymers such as polystyrene and polybutadiene. Our work shows that this technique is general and can be applied to more polar polymers. 

Parts a and b of Figure 5.5 show the C-NMR spectra of the compounds corresponding to n = 1 and 2, respectively. The former was prepared by ozonolysis of 4-vinyl-l-cyclohexene, and the latter obtained by GPC fractionation of the ozonolysis product of polybutadiene. It is clear that all the hydroxyl groups have been esterfied with TFAA. 

The peak of the 1,4-1,4 sequence was not detected because it overlapped with an intense impurity peak. A small shoulder observed at the peak of 164 ml is presumed to arise from unreacted hydroxyl groups that partially remained in the acetate derivatives. Therefore, the reactivity of acetic anhydride toward polyols is lower than that of TFAA. The GPC chromatogram of acetate derivatives of the ozonolysis products from polybutadiene showed a poorer separation than that of TFAA derivatives due to the... 

Ba/Mg/Al catalyst system discussed above can be readily converted into a variety of functional end groups. One of the most useful and widely used functionalization reactions is hydroxyethylation using ethylene oxide, as shown in Fig. 14. Here, a mono-hydroxyl-terminated high-fran polybutadiene was prepared by adding a small amount of ethylene oxide to a solution of carbanions, followed by hydrolysis. This particular example demonstrates the ability to attach hydroxyl groups molecularly to a crystalline polybutadiene. The use of a bifunctional diorganomagnesium could provide a very useful tele-chelic polymer for further extension to form a rubber network. 

Polybutadiene has been modified in several ways with MA. In one case, poly(butadiene) with terminal hydroxyl groups have been treated with MA and epoxides to prepare polybutadiene-polyester block copolymer. 

Infrared spectroscopy has also been used to determine hydroxyl groups in polyethers [20], polyethylene ether carbonate [21], and carboxy terminated polybutadiene [22, 23] and hydroxybutadienes [24]. 

Low molecular weight polybutadiene and butadiene-acrylonitrile copolymers terminated with carboxyl, vinyl, amine, epoxy, phenol, and hydroxyl groups have been widely used as toughening agents both for epoxy and polyester resins. Thermally reactive isoprene-acrylonitrile and ethylacrylate-butylacrylate copolymers have also been used [82,83]. 

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