To investigate the nucleation effect of hydroxyl-purified multiwalled carbon nanotubes (MWNTs-OH) in poly(p-phenylenesulfide) (PPS), a series of composites were prepared by blending PPS with MWNTs-OH at 1, 2, and 3 wt %, respectively. Under SEM observation MWNTs-OH were found homogeneously dispersed in the PPS matrix. DSC thermograms revealed that the enthalpy (?Hc) of the composites increased with increasing MWNT-OH content, whereas the crystallization temperature (Tc) decreased progressively. The decrease in Tc was in accordance with the smaller crystallite size determined with WXRD characterization, and the increase in ?Hc was evidenced by FTIR and XPS analyses. The higher ?Hc shows that MWNTs-OH serves as a nucleating agent, providing sufficiently multiplied sites for crystal growth. The lowering of Tc was attributed not only to MWNTs-OH network hindrance to PPS chain fusing rearrangement, but also to a poorer affinity between MWNTs-OH and PPS; both effects coordinately govern Tc of PPS/MWNTs-OH composites. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012