Both techniques can be used successfully, but DMA should be more precise.

Thanks for the answer, can you guide me with some literature evidence.

The following papers may be useful for you:

1- Gauthier M, Tichagwa L, Downey JS, Gao S. Arborescent graft copolymers: highly branched macromolecules with a core–shell morphology. Macromolecules 1996;29:519–27

2- Bernard J, Schappacher M, Viville P, Lazzaroni R, Deffieux A. Synthesis and properties of PS–PEO core–shell amphiphilic dendrigrafts. Polymer 2005;46:6767–76

3- Yin Y, Yang L, Yoshino M, Fang J, Tanaka K, Kita H, et al. Synthesis and gas permeation properties of star-like poly(ethylene oxide)s using hyperbranched polyimide as central core. Polym J 2004;36:294–302

Detection of Tg signal in DSC would  depend on the state of the core-shell polymer which is formed during polymerization. You may  try the following taking 10-15 mg of sample in DSC pan.

1. Heat the sample to destroy the structure formed to bring it to  amorphous  form, quickly cool ad rescan.

2. Heat the sample till  lower Tg+10 OC, cool and heat again to observe second Tg.

It is also important to know the melting points of both the polymers. Melting of one could  affect the  morphology of other and over all signal may not be of help.

TMA also could be of help. A pellet made out of the powder and  subjecting it to heating profiles could give changes in linear temperature expansion at the Tg of the polymers. All the best.

Dear All,

Thanks for your valuable suggestion, it will help me on deciding either of the technique.

I've relied on DSC (and sometimes modulated version for greater sensitivity) all my professional life for so-called Tg measurements.  We always found DSC to be preferable to all other forms of thermal analysis because of speed of run, simplicity of technique and reproducibility.  We also found the fewest artifacts with DSC. 

My colleagues and I spent ~5 years developing techniques for synthesis and proof of structure for core/shell latexes, with considerable success.  See authors Erickson and Seidewand for synthetic issues (e.g. ACS Symposium Series No. 165: Emulsion Polymers and Emulsion Polyumerization, pp. 483+, 1981).  See Floyd in Proceedings of IUPAC Symposium on Macromolecules, Amherst, MA., June 12-16, 1982 for performance comparisons between core/shell, latex blend, and comparable overall composition copolymers.   See Neag, et al. for a variety of papers on DSC techniques during the 1980's and beyond. 

Before embarking on testing of alleged core/shell structures, it would be useful to first prove the morphology of the sample under consideration.  A substantial number of references to core/shell structures in the literature are simply wrong in their presumptions.  By the way, the same is true for IPN's (interpenetrating polymer networks).  My point is that it is pointless to attempt to measure or discuss structures that have not been first proved by other means. 

Our primary proof of core/shell structure was provided by following particle size as a function of time during the 2-stage sequential emulsion polymerization.  Since no second generation of particles was detected during the second stage, the composition was concluded to be contained within the initial particles formed in stage I. 

The proof of core/shell morphology was provided by simple minimum film formation measurements (MFT) that showed that the MFT for the core/shell latex closely followed that of physical blends of the two latexes in the same proportions.  Meanwhile, comparable copolymers of equal overall composition and solution blends of the two compositions produced substantially higher Tg's and MFT's. 

There was a filler effect (slight increase in Tg and MFT) caused by the addition of the harder composition, which was  a bit more significant in the blends than in the core/shell systems, which reinforced the thought that we were indeed dealing with core/shell structures. 

We were always seeking film-forming latex compositions, so our samples were scraped from pre-formed films of the latexes in question.  This introduced an artifact:  a  relaxation of the scraping in the sample pan to conform to the pan geometry -- shows up as an endotherm just above Tg, which disappears on second heating run. 

Although nominally amorphous, our latexes routinely showed some evidence of crystallization that increased over time in the dried films, which manifested itself as a melt temperature above the Tg of the softer composition that disappeared after the first run.  [DSC was always run in successive pairs, to observe the disappearance of transitions during the first run.]   

To sum up:  don't assume your structure -- prove it before continuing.  Then make sure that you're using the proper alternate compositional and structural comparisons as reference points to build your case logically,  Only then will film (or other) properties be of much value.