Nanoscale Res Lett (2009) 4:420–430 Thermogravimetric analysis (TGA) of gel ﬁlled systems was done using TA Instruments (Luken’s Drive, New Castle, DE, USA) TGA-Q 50. The samples (10 ± 2 mg) were heated from ambient temperature to 700 C in the furnace of the instrument under nitrogen atmosphere at a ﬂow rate of 60 mL/min. The experiments were done at 10 C/min heating rate and the data of weight loss versus temperature were recorded online in the TA Instrument’s Q series Explorer software. The analysis of the thermo- gravimetric (TG) and derivative thermogravimetric (DTG) curves was done using TA Instrument’s Universal Analysis 2000 software version 3.3B. In the present study, the temperature corresponding to 5% weight loss was taken as initial degradation temperature (Ti) and the temperature corresponding to the maximum rate of degradation in the derivative thermogram was considered as peak degradation temperature (Tmax). The experimental error limit was within ± 1 C. Results and Discussion Characterization of Crosslinked Nanogels Figure 1a–b compares the particle size distribution (PSD) of the control SBR and NR lattices and their sulfur Fig. 1 Particle size distribution by DLS method for a SBR and SBS gels and b NR and NS gels 423 prevulcanized gels, as determined by the DLS method, respectively. The gels and the virgin SBR latex show wide PSD with particle diameters ranging from 35 to 139 nm (Fig. 1a). In the case of NR latex gels, it reveals also a broad distribution of particle sizes for all the systems studied, with a size range of 122–360 nm, which is within the expected size range reported in the literature [22]. Apparently, both the NR and SBR gels give very similar PSD than that of their respective control latex. Zavg values, the mean hydrodynamic particle diameter, of SBR and NR latex gels are listed in Table 2. The Zavg for NR gels lies between 205 nm and 221 nm as against 220 nm of the control NR latex. For SBR gels, these values range from 87 to 94 nm, while Zavg of SBR latex is 85 nm. PSD and Zavg do not change much during the course of prevulcanization reaction. This is believed to be due to the fact that sulfur crosslinking during prevulcanization occurs inside the individual latex particles and does not alter the Zavg and the PSD greatly [23]. The increase in sulfur to accelerator ratio has no apparent effect on the dimensions of the gel parti- cles, although there is a slight increase in Zavg for SBS gels without any particular trend. Tapping mode atomic force microscopy (AFM) tech- nique was used to visualize the individual gel particles, as illustrated in Fig. 2a–b. Here, NS3 and SBS3 gels have been shown as representative systems. The particle diameters in Z-avg diameter (nm) Gel content (%) Crosslink density 9 104 (gmolcm-3) Young’s modulus (MPa) E.B. (%) E0 at 25 C (MPa) Table 2 Various properties of the gels Gel type NS0.5 NS1 NS2 NS3 SBS0.5 SBS1 SBS2 SBS3 205 219 214 221 94 92 87 90 88.0 94.2 96.3 97.4 89.0 92.5 95.1 97.0 0.36 0.75 1.00 1.11 0.80 1.50 2.20 2.40 T.S. (MPa) 12.7 15.8 17.0 18.9 2.1 2.8 3.1 3.2 1.30 1.45 1.74 1.98 3.04 3.42 3.85 3.90 1200 1170 1125 1120 430 405 370 360 1.56 1.65 2.10 2.42 0.80 1.28 2.31 2.63 Tg ( C) -53.4 -51.6 -50.5 -48.6 -38.0 -37.1 -35.9 -31.0 123