EFFECT OF POLYMERIZATION DEGREE ON MICROSTRUCTURE OF POLYETHYLENE GLYCOL STUDIED BY POSITRON ANNIHILATION

EFFECT OF POLYMERIZATION DEGREE ON MICROSTRUCTURE OF POLYETHYLENE GLYCOL STUDIED BY POSITRON ANNIHILATION 1 first-author 1 1 1 2 Wuhan University, Wuhan 430072, China Wuhan University, Wuhan 430072, China Hubei Provincial Institute of Chemistry Research, Wuhan 430074, China Hubei Provincial Institute of Chemistry Research, Wuhan 430074, China Positron lifetimes in polyethylene glycol (PEG) polymer have been measured as a function of polymerization degree N ( N = 25-500). It is observed that all the positron parameters are strongly dependent on N when N ≤ 250, and then tend to constant levels when N ≥ 250. The variations of the longest-lived component ( I 3 , τ 3 ) show that the size of free-volume holes has a minimum at N = 100 and the hole concentration deereases with N . These trends may be due to the variations in crystallinity, the chain ends, entanglements and the Van der Waals interaction between segments. The variations of the second component ( I 2 , τ 2 ) with N reflect the changes of defect properties in crystalline regions of PEG. Potitron annihilation Polyethylene glycol Free-volume hole Defect REFERENCES Ferry J D . Viscoelastic properties of polymers . New York : Wiley , 1970 Viscoelastic properties of polymers Jean Y C . Microchem J , 1990 ; 42 : 72 Microchem J Lin D , Wang S J . J Phys , 1992 ; C4 : 3331 J Phys Liu L B , Yee A F , Giley D W . J Polym Sci , 1992 ; B30 : 231 J Polym Sci Chuang S Y , Tao S J . J Appl Phys , 1973 ; 44 : 5171 J Appl Phys Singh J J , Eftekhari A . Bull Am Phys Soc , 1992 ; 37 : 207 Bull Am Phys Soc Yao N , Li Y , Nu X . Eur Polym J , 1992 ; 28 : 831 Eur Polym J Kirkgaard P , Eldrup M , Mogensen O et al . Comput Phys Commun , 1981 ; 23 : 307 Comput Phys Commun Hautojarvi P , Positrons in Solids . Berlin : Springer-Verlag , 1979 Positrons in Solids The Project Supported by National Natural Science Foundation of China 1993-11-01 2021-02-05 1993 Nuclear Science and Techniques 4 4