Is it a good option to pursue B.Tech in polymer science and chemical technology as I want to opt for civil services after it?

For getting into civil service exam you just need a degree from any institute, it doesn't matter what your branch is, so I can say that it will be a good option for you to choose polymer science and chemical technology in your B.Tech and also that subject has good scope.

Subject is not aligned with any of Civil Services optional paper. Therefore, it will not give any direct benifit in cracking Civil Services Examination. But it is a good stand by career option if you are unable to crack Civil Services Examination. India has well developed Polymer and Chemical engine