The adsorption of poly(ethylene a-phthalate) from chloroform solution on glass powdcr and aluminum oxide was studied . The adsorption of a number of fraction s vary in{T in number ave. rag~ mol ecular weight from 97 0 to 6250 showed a decrease in the mol~s of poly~ner a d sorbed with mcrease m mol ec ular weight. The results are interpreted to indicate that this polymer molecule lies in a relatively flattened conformation on the gla ss s urface. More polymer was a dsorbed on glass powder at 50°C than [l,t 0 °C. Adsorption on glass powder that had been ou tgassed to remove adsorbed water was less than on untreated glass. Initia l adsorptIOn at one temperature followed b y exposure at t he other temperature r esulted in complete reversibility of sorption on the untreated glass. DecreaSing th e temperat ure from 50 to 0 °C resulted in desorption from t he outgassed glass, but increasing t h e temperature did not res ult in addi tional adsorption. These dir· rcrences are ascribed in part t o adsorption across an a dsorbed water layer on t he untreated glass. An explanat ion fo r t hc "one-direction reversibili ty" observed for t h e outgassed glass is presented.
I . IntroductionMost studies of polymer adsorption h ave been concerned with r elatively high molecular weight materials. Their b ehavior is, of course, very different from that of small molecules. Molecules of intermediate molecular weight are also of interest, but have not b een extensively investigated. In previous work in thi.s area, the adsorption of a series of r elatively low molecular weight poly (ethylene glycols) on a porous carbon [1] 3 and of several polyesters with molecular weights of the order of 4000 on glass, silica, and alumi.na [2] has been studied. The adsorption isotherms for the polyesters were not n early as steep at low conccntrations as were those for higher JJ?-olecular weight polymers; a plateau was not attallled until relatively high solution concentrations were reached.The adsorption-desorption behavior of polymer molecules has been of interest, in part, b ecause of the information implied regarding the conformation of the polymer molecule and interactions 'with the surface. Polymer molecules have been reported to adsorb relatively rapidly [2, 3, 4, 5] on nonporous surfaces, although some r ecent measurements indicate that this is not necessarily so under all conditions [4,6]. A recent theoretical treatment [7,8] has con~luded that times to equilibrium are long, caused m part by r earrangements of the molecule at . the surface. The times required for desorption, usmg the ame solvent, can be of a different order of magnitude from those required for adsorption. For some systems no desorption occurs within practical units of time (see, e.g., ref.[2]) , while for others some desorption does occur [3,5,6]. In one study,
601S?xhl ct extraction removed only negligible amoun Ls of polystyrene that lutd been adsorbed on c