Poly(hexamethylene succinate-co-hexamethylene fumarate)s (PHSF) with low hexamethylene fumarate content (C-HF, between 0 and 18 mol%) were prepared and employed to explore the effect of intersegmental interaction in crystalline lattice on the polymorphism phenomenon. Wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) results demonstrate that the crystal modification of PHSF exhibits not only C-HF-dependent but also crystallization temperature (T-c) dependent. Both high CHF and high TT benefit the formation of orthorhombic modification, while low CHF and low TT benefit the formation of monoclinic modification. More intriguingly, the specific "C=C-C=O center dot center dot center dot H-C=C" hydrogen bonds formed between fumaryl units provide a direct way to regulate the polymorphism from perspective inside chain structure. When CHF is between 8 and 12 mol%, the crystal modification of PHSF is determined by formation of intersegmental hydrogen bonding interaction or not through varying T-c At high T-c the specific hydrogen bonds form and render the formation of orthorhombic crystal; while at low T-c, only van der Waals forces remain and PHSF chains crystallize into monoclinic crystal. The content of carbonyl group belonging to fumaryl in polyester chain is a key factor for the formation of hydrogen bonds and the selection of crystal structure during crystallization. Additionally, the orthorhombic crystal shows higher equilibrium melting point than monoclinic crystal; and the monoclinic crystal can transform to orthorhombic crystal by annealing, revealing that orthorhombic crystal is more thermally stable. (C) 2016 Elsevier Ltd. All rights reserved.