Under conditions of plasma polymerization, we are dealing with the “reactive” or “self‐exhausting” rather than the “nonreactive” or “non‐self‐exhausting” gas phase (plasma). Therefore, many parameters that define the gas phase, such as system pressure and monomer flow rate, which are measured in the nonplasma state (before glow discharge is initiated), do not apply to a steady state of plasma, the conditions under which most of the studies on plasma polymerization are carried out. Consequently, information based on: (1) the polymer deposition rate measured at a fixed flow rate and discharge power, (2) the dependence of deposition rate on flow rate at fixed discharge power, or (3) the dependence of deposition rate on discharge power at fixed flow rate, does not provide meaningful data that can be used to compare the characteristic nature of various organic compounds in plasma polymerization. The significance and true meaning of experimental parameters applicable to conditions of plasma polymerization are discussed. The most important feature is that plasma polymerizations of various organic compounds should be compared at comparable levels of composite discharge power parameter W/FM, where W is discharge power, F is the monomer flow rate (given in moles), and M is the molecular weight of a monomer.

Poly(L‐lactic acid) sheets, prepared by melt extrusion, were treated with O2−, He−, and N2−plasmas generated in radio frequency (RF) at 13.56 MHz. Atmospheric pressure discharge at 20 kHz in helium was also applied to the modification of the sheets. The surface of the PLLA sheets was etched to form the characteristic morphology, and the patterns were different depending on the type of plasma. Polar groups composed of –COOH and –OH were incorporated by plasma treatment, and the surface became wettable. Surface modification became effective after a short treatment period, e.g., 30 seconds. Receding contact angles (θr) changed remarkably, and the surface properties were closely related to the increase in the surface energy of the polar contribution (γsp). Biodegradation of the poly(L‐lactic acid) sheets was not enhanced practically, even though the surface became hydrophilic after plasma treatment.

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The sheets prepared by the extrusion of the melt of poly(butylene succinate) were treated with inorganic gas plasmas. Bionolle, the commercially available polyester, was also used, and the treatment effects were compared. Plasma susceptibility by the continuous plasma of 13.56 MHz and by pulsed plasmas was evaluated by the weight loss rates by etching. Advancing and receding contact angles of water (θa , θr ) on the plasma‐treated sheets were obtained by the Wilhelmy method. Decay of hydrophilicity was considerable in θa , but θr was less changed. The biodegradation was examined by the preliminary soil‐burial tests. The polymer sheets were biologically degraded, and the characteristic morphology appeared on the surface according to the SEM observation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1121–1129, 2000