## 2 Results and Discussion
### Synthesis of Oil Soluble Hyperbranched Polymers
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Entry**} & \multirow{2}{*}{**Structure**} & \multicolumn{2}{c}{**CTA**} & \multirow{2}{*}{**Time**} & \multirow{2}{*}{**Yield a**} & \multirow{2}{*}{**M\({}_{\text{n}}\) b**} & \multirow{2}{*}{**D b**} \\  & & **Oligomer** & & & & (\%) & (g mol\({}^{-1}\)) \\ \hline
1 & Random & PhCoBF & 35 & 53 & 3650 & 4.9 \\
2 & Semi-Block-like & Crude LMA & 35 & 66 & 3700 & 102.7 \\
3 & Block-like & Purified LMA & 35 & 65 & 4400 & 58.4 \\
4 & Block like & Purified LMA & 10 & na c & 2500 & 5.5 \\
5 & Block like & Purified LMA & 20 & na c & 3300 & 6.7 \\
6 & Block-like & Purified LMA & 30 & na c & 4200 & 74.7 \\
7 & Block-like & Purified LMA & 40 & Gel & Gel & Gel \\ \hline \hline \end{tabular}  
* determined gravimetrically; b determined via GPC, c na not available—these results were from small kinetic samples taken at time points from a reaction that was allowed to run through to the gelation point. Thus, a representative gravimetric yield could not be obtained from these small samples.  
\end{table} 
Table 2: Yield and molecular weight data of the copolymers produced. be the lowest (Table 2, entry 1), while the block-like polymers D values raised to \(\sim\)50 and finally the semi-block-like typically had D values greater than 100. The lower M\({}_{\rm w}\) of the block-like structure compared to the semi-block-like was proposed to be due to the higher concentration of the CTA moieties in the distilled reagent mixture compared to the crude. High D values are characteristics of HB polymers due to the nonlinear nature of their structure. Thus, they do not have a proportional relationship between hydrodynamic volume and molecular weight. Equally, HB polymers, due to their branched structures, do not exhibit the same relationship between hydrodynamic volume and molecular weight as linear materials. Thus, their passage through the GPC column will be altered, and so the predicted M\({}_{\rm n}\) and M\({}_{\rm w}\) values, which are based upon comparison to the commercially produced linear standards, will not be correct. However, these values were unexpectedly high, especially for soluble polymers. Thus, additional sets of experiments were prepared to identify if these D values were repeatedly achieved using this technique. These experiments involved the isolation of \"kinetic\" samples at 10-, 20- and 30-min points from a repeat reaction that was run through to the gelation point. Results from a reaction using purified LMA oligomers are shown as Entries 4-6 in Table 2. This data showed that the D did repeatably rise to the 50-70 region as the reaction reached approximately 30 min. Meanwhile, the random copolymers' lower D value was attributed to the reaction being in the early stages of hyperbranching when it was quenched. This was due to greater reaction rate retardation caused by the high efficiency of the CCTP mediating agent. Its efficiency was also thought to result in very short interbranch distances. These factors associated with PhCoBF use were also thought to explain the lower polymer yield compared to the semi-block-like/block-like reactions. As a result of these materials being solvent/base oil soluble, they were passed on into application testing, although it is proposed that the actual value of the M\({}_{\rm n}\) and M\({}_{\rm w}\) molecular weights is relatively meaningless with such large D values. Rather, it was proposed that the differences in the polydispersities exhibited by the polymer mixtures may be a better \"analytical value\" by which to compare these materials. Ongoing work is trying to define alternative routes to quantify these types of large D materials.