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A: Rarely. Chegg has expert answers for undergraduate physics, not for specialized graduate polymer physics. You will likely waste a subscription fee.
However, the best "solution manual" is a study group. Work through the problems with peers, cross-check your answers against the fragments available online, and most importantly, challenge the manual when you disagree. In polymer physics, the literature itself is full of approximate solutions. Polymer Physics Rubinstein Solutions Manual
Use the manual to pass your course. Use the process to become a scientist. Note to educators: If you are teaching from Rubinstein & Colby, consider writing an "answer key" for your specific homework assignments rather than circulating a full solutions manual. This maintains academic integrity while helping students struggling with the statistical mechanics formalism. A: Rarely