Synthesis and Characterization of Allyl-Functionalized Octa-Arm PIB Stars

Synthesis and Characterization of Allyl-Functionalized Octa-Arm PIB Stars 

The stars were characterized by GPC (LLS) and NMR spectroscopy. The RI traces (see Fig. 5) showed the formation of monomodal narrow dispersity stars. Molecular characteristics of two representative samples are summarized in Table 2. According to NMR evidence (Fig. 6), the arms were quantitatively functionalized with allyl groups. The end-functionality of the stars was calculated by comparing the integrated peak area of the core protons [aromatic (5= 6.82 ppm), -CH2- (6=4.0 ppm)] and chain end allyl protons (-CH2- (5=2.0 ppm), -CH= (5=5.8 ppm), =CH2 (5=5.1 ppm), and was found to be 8.1, after correcting for the presence of -10% linear contaminant. Quantitative allyl-functionalization is direct proof for the formation of the octa-arm stars. 

In summary, a core-first method was used to prepare allyl-end functionalized octa-arm PIB stars by end quenching the living PIB stars by the use of allyltri-methylsilane. Characterizations by NMR and GPC are consistent with the expected structure and show close to quantitative end-functionalization. 

Initiator 1 molX10 Star molecular weight g/molXlO Arm molecular weight g/molX 10 End Functionality of Star  

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