The isothermal crystallization behavior of a poly(bisphenol A-co-decane) (BA-C10) at 35 degreesC was studied in situ using polarized optical microscopy, atomic force microscopy (AFM) and Fourier transform infrared spectroscopic (FT-IR) measurements. Real-time FT-IR investigation revealed that an increase in regularity as well as intermolecular chain packing of certain functional groups of the BA-C10 main chains during crystallization. Our real-time AFM and FT-IR results provide an understanding of the relationship between the polymer morphology and the chain conformation during polymer crystallization.