Carboxy telechelics

Fig. 17. Addition product of tetra-n-butoxy-titanium to carboxy telechelic polybutadiene...

The functional initiators were prepared many years ago and were used for the synthesis of polybutadiene carboxy telechelic by the Thiokol Company [74] according to the following scheme ... 

Synthesis and Characterization. The synthesis of carboxy-telechelic polyisoprenes was carried out as described previously[7], in tetrahydrofuran at -78°C using sodium naphthalide as initiator. Approximately 2-3 units of a-methylstyrene per living end were added after completion of the Isoprene polymerization to reduce the reactivity of the chain ends, which were then terminated by the addition of gaseous... 

Figure 1. Stress-strain behavior of carboxy-telechelic polyisoprenes, (a) Ca and Sr, (b) nP, Zn, and Cd. (Reprinted from ref. 11. Copyright 1988 American Chemical Society.)...

Figure 1. Desmeared, background-subtracted SAXS patterns for carboxy-telechelic polyisoprenes. Curves are offset 1200 intensity units for clarity.

In contrast, for carboxy-telechelic butadiene swollen by toluene, the small angle peak decreases both in intensity and in scattering angle (45). Comparison of the microscopic with macroscopic swelling indicated that the deformation in these... 

Polymer Preparation. Two bifunctional (telechelic) polymers were used in this study. Carboxy-telechelic polybutadiene (PB) is commercially available from B. F. Goodrich (Hycar CTB 2000X156) with molecular characteristics of Mn=4,600, Mw/Mn= 1.8, functionality 2.00 and cis/trans/vinyl ratio of 20/65/15. Carboxy-telechelic polyisoprene (PIP) was prepared by anionic polymerization in THF at -78°C with a-methylstyrene tetramer as a difunctional initiator. The living macrodianions were deactivated by anhydrous carbon dioxide. Five polymers werejjrepared with Mn=6,000 10,000, 24,000, 30,000 and 37,000 having Mw/Mn=sl.l5 a microstructure ratio of 3, 4/1, 2 of 65/35, respectively, and a functionality >1.95. 

Selective transesterification of the chain-end ester groups leading to carboxy-telechelic oligomethacrylates. 

Styrene is probably the most used monomer in DEP conditions [34], Recently, some authors developed the synthesis of carboxy-telechelic polystyrene (PS) through DEP [35-37] by using ACVA. In a recent publication [38], we focused on developing the synthesis of carboxy-telechelic PS by improving the experimental conditions of DEP (Scheme 6). 

Scheme 6 Synthesis of carboxy-telechelic polystyrene by dead-end polymerization (DEP)...

The synthesis of carboxy-telechelic PS by DEP is now well established. But the major breakthrough in this synthesis certainly concerns the kinetics approach and the prediction of the cumulative degree of polymerization. 

Table 6 Synthesis of carboxy-telechelic ethyl hexyl acrylate in DEP conditions with ACVA...

This work focuses on HTP resulting from the neutralization of carboxy telechelic polymers (eq. 1), although polymers with sulfonic end-groups have also been investigated. 

TABLE I. Relative viscosities at different concentrations in toluene at 25°C, for carboxy telechelic polybutadiene (Hycar CTB from Goodrich) mixed with stoichiometric amount of magnesium methoxide. 

The carboxy telechelic PBD commercialized by BF Goodrich un r trade mark ycw CTB 2000 x 156 was lai ely used in this work (M ) = 4,600 Myy/Mn = 1.8 functionality = 2.01 and microstructure cis/trans/vinyl = 20/65/15). Carboxy telechelic polyisoprene (PIP), poly a-methylstyrene (PMS) and poly tert.butylstyrene (PTBS) were prepared by anionic polymerization in THF at -78°C. 

In nonpolar solvent, the neutralization of the carboxy telechelic polymers considered in this study generally results in the formation of homogeneous gels (10 wt% of solids), which can however suffer demixing upon subsequent dilution. For instance, a phase separation occurs systematically when PBD (Hycar CTB from B. F. Goodrich) is neutralized with Be and A1 derivatives, respectively. This phenomenon is quite reversible since a homogeneous gel is again observed when the excess... 

When the molecular weight distribution of the original carboxy telechelic polymer is very narrow, the increase of the solution viscosity is very sharp and the critical concentration for gelation (Cgel) is accurately determined by the vertical asymptote of the log n rel vs. concentration curve. 

The intrinsic viscosity [r ] of the non-neutralized carboxy telechelic prepolymers has been measured in toluene at 25°C and the calculated values of gpg reported in Table IV, together with the... 

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