Glass transition behavior of hydrogen bonded polymer blends of poly(vinyl phenol) (PVPh) and poly(ethylene oxide) (PEO) is systematically investigated using normal differential scanning calorimetry (DSC) and recently developed multifrequency temperature-modulated DSC (TOPEM)

in combination with Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) techniques

focusing on the effect of the PEO molecular weight on the spatial and dynamic heterogeneity. It is found

for the first time

that both the glass transition temperature (

T

g

) and activity energy (

E

a

) of the blends strongly depend on PEO molecular weight

and a common turning point

which separates the rapid and slow increasing regions

can be found. The interchain hydrogen bonding interactions

both determined by FTIR measurements and obtained from the Kwei equation

decrease with increasing PEO molecular weight

indicating a decrease of the componential miscibility. A series of parameters related to the microscopic spatial and dynamic heterogeneity

such as the activity energy

fragility

nonexponential factor and the size of cooperatively rearranging regions

are calculated from frequency dependency complex heat capacity measured using TOPEM. It is found that each of these parameters monotonically changes with increasing the PEO molecular weight during the glass transition process

demonstrating that hydrogen bonding interaction is the key factor in controlling the spatial and dynamic heterogeneity

thus the glass transition. NMR relaxation results reveal the existence of obvious phase separation large than 5 nm

implying that the cooperatively rearranging regions should be closely related to the interphase region between the two components. The above obtained origin and evolution of spatial and dynamic heterogeneity provide a new insight into the glass transition behavior of polymer blends.