Functionalized elastomer

[0065]Homopolymerizations of BD were performed to optimize polymerization conditions for high stereoselectivity and to assess the influence of the diene:Nd ratio on the molecular weights and molecular weight distributions of the obtained polymers. 5 μmol Nd(BH4)3.(THF)3 were activated with 1 equiv. of MgBuz in the presence of different amounts of BD in toluene (Table 1, entries 1-3). Polymerization at 60° C. for 5 h yielded in all cases highly stereoregular 1,4-trans-PBD (>95 mol % trans-units). The molecular weights of the obtained polymers are close to the theoretically calculated molecular weights (for a polymerization where only one polymer chain per Nd is formed) and increase linearly with increasing BD:Nd ratio. Although GPC analyses indicate a bimodal molecular weight distribution (cf. SI), all molecular weight distributions are narrow (Mw / Mn=1.3-1.6). Hence, a controlled character of the polymerization can be assumed. DSC analyses of the polymers gave the typically two disti...

[0066]Copolymerization with Polar Functionalized Dienes.

[0067]The functional group tolerance of Nd(BH4)3.(THF)3 activated with MgR2 in diene polymerizations was tested with comonomers 1-5 (Table 1-A, entries 7-12).

[0068]Chart 1: Polar functionalized dienes used in copolymerizations with butadiene and isoprene.

TABLE 1-Ayieldcomon.comon.Mnb)1,4-trans-cat.timediene comon.[mg]incorp.a)conv.[103 gTmc)contentd)entry[μmol][h][mmol][μmol](%)[mol %][%]mol−1]Mw / Mnb)[°C.][%] 7 554.6 BD150152 (61)1 3.973431.850 / 7294 8 554.6 BD170195 (79)2 n.d.e)n.d.e)461.648 / 9394 9 554.6 BD150222 (89)3 3.699443.047 / 6194106056.2 IP430484 (92)3 7.2997.71.3n.d.9611 554.6 BD 0.162084 3.482431.950 / 739312 554.6 BD 0.151965 3.380473.049 / 7193Polymerization conditions: Nd(BH4)3•(THF)3:MgBu2 = 1:1, T = 60° C. in toluenea)determined by 1HNMRb)determined by GPC in THF vs. PS standards.c)determined by DSCd)determined by 13C NMRe)incorporation not determined because comonomer incorporation signals are overlapped by the polym...

[0071]Chain-End Functionalization by Quenching.

[0072]The second part of the functionalization strategy aims at the reaction of reactive metal-carbon bonds present with a suitable quenching reagent (Scheme 1).

[0073]We tested four different quenching reagents, Si(OEt)4, Ph2PCl, B(OEt)3, and P(O)(OEt)3 towards their reactivity with the aforementioned metal-carbon bonds. For this purpose, polymerizations run with an IP:Nd ratio of 100:1 were terminated by the addition of the quenching reagents (cf. Table 1, entries 5 and 6, for examples with Si(OEt)4 and Ph2PCl). The reaction mixture was stirred at the polymerization temperature until it became colorless. The polymers were isolated by precipitation in dry acetonitrile (polymers quenched with Si(OEt)4, B(OEt)3, or P(O)(OEt)3) or acidified MeOH (Ph2PCl-modified) followed by drying under reduced pressure. To verify the functionalization by quenching, the polymers were subjected to a thorough analysis by means of NMR spectroscopy. 1H and 13...