Nanoscale Res Lett (2009) 4:420–430 Effect of Gels on the Dynamic Mechanical Properties Figure 8 shows the temperature dependencies of storage modulus (E0) for SBR nanogel ﬁlled NR systems. Over a long range of temperatures, the SBS1 ﬁlled systems show much increased storage modulus compared to the neat NR. Again, at 25 C, more than 1.51 times improvement in log (storage modulus) can be observed with 4 phr of NS1 gel compared to the control SBR (shown as Figure S3 of Supplementary Information). The improvement in storage modulus is higher in the case SBS1 ﬁlled NR systems, especially in the glassy to sub-ambient region (Fig. 8). However, in the case of NS1 ﬁlled SBR systems, the dif- ference in storage modulus values of gel ﬁlled systems with neat SBR is much more prominent in the rubbery plateau region, due to the lesser extent of aggregation in the case of NS1 compared to SBS1(Fig. S3). The storage modulus increases steadily on changing the gel loading from 2 to 16 phr in the transition region while in rubbery region, in general, it has increased marginally for SBS1 ﬁlled NR systems. Similar trend also can be seen in NS1 ﬁlled SBR systems. The substantial increase in storage modulus of the gel ﬁlled systems can be attributed to the presence of three- dimensional networks of crosslinked gel which provide greater resistance to dynamic deformation. Figure 8 (inset) also illustrates the temperature depen- dencies of loss tangent of SBR nanogel ﬁlled NR systems. With the addition of 16 phr SBS1 gel in NR, Tg of NR shifts towards higher temperature by 4 C, accompanied by steady reduction in tan d peak height. It is very interesting to mention here that upto 8 phr (*7.4 wt%) of SBS1 gel loading in NR generates single Tg corresponding to NR. However, at 16 phr (*13.9 wt%) gel loading, two distinct 429 peaks can been seen easily (one with a broad shoulder peak at -32.8 C for SBS1 gel). This could be attributed to the macro phase separation of gels with matrix at relatively higher loading. Similar trend is also observed for NS1 ﬁlled SBR systems (see Figure S4 of Supplementary Informa- tion). For example, in SBNS1/16, a small peak appears at -53 C for NS1 along with another one at -33.3 C for SBR. With addition of NS1 gel in SBR, Tg shifts from -39.2 C in SBR to -32.0 C in SBNS1/8. The presence of crosslinks in the raw rubber matrix hinders the segmental motions of the polymer chains and therefore, Tg is pro- gressively shifted to higher temperature with the increase in gel loading. Effect of Gels on the Thermal Properties Typical TG curves for SBR nanogel ﬁlled NR is shown in Fig. 9. These TG curves correspond to predominant single- step degradation with well-deﬁned initial and ﬁnal degra- dation temperatures and may be a result of a random chain scission process. Normally addition of particulate ﬁllers in neat rubber matrix is accompanied by the enhancement of thermal stability for the latter [31]. In this case also, pres- ence of chemically crosslinked SBR nanogels improves the thermal stability of the neat NR considerably (Fig. 9). Both initial (Ti) and ﬁnal decomposition (Tf, corresponding to 95% weight loss) temperature of NR increase gradually with the increase in SBR gel loading. For example, Ti (temperature corresponding to 5% weight loss) in NRSBS1/ 16 increases by 9 C from that of NR. This could be due to the inherently better thermal stability of the SBR gels compared to NR. However, in the case of NR gel ﬁlled SBR (given as Figure S5 of Supplementary Information), although there is a decrease in Ti initially with the addition Fig. 8 Variation in Log (storage modulus) vs. temperature for SBS1 gel ﬁlled NR systems. Variation of Tan d (loss factor) vs. temperature for the same systems is shown as inset Fig. 9 TGA thermograms of SBS1 gel ﬁlled NR systems. DTG plots of the same systems are shown as inset 123