A study of the glass transition of polypropylene surfaces by sum-frequencyvibrational spectroscopy and scanning force microscopy

Sum-frequency generation (SFG) vibrational spectroscopy and scanning force microscopy (SFM) were used to probe structural changes of atactic polypropy lene (APP) and isotactic polypropylene (IPP) surfaces in the glass transiti on. The results indicate that below the glass transition, the surface polym er chains are better oriented with the CH2 groups pointing outward and the surface elastic modulus is higher. The SFG and SFM results correlate well i n the transition towards the glass phase. No discernible difference between the glass transition temperatures of the bulk and surface was observed. (C ) 1999 Elsevier Science B.V. All rights reserved.