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

SynopsisOwing to the unique mechanisms operative in plasma polymerization, a thin layer of plasma polymer deposited on the surface of a substrate shows a tendency to expand, indicating an internal stress in the layer. This stress, a,, has been estimated from the observed curling of composite membranes in which the thickness of the plasma coating, d , is much smaller than the thickness of a flexible substrate, D , according to the relationwhere R is the radius of the roll into which the composite films curl up and E is the modulus of the substrate polymer. The stress us is found to depend on the kind of monomer used and to be of the order of magnitude 10s-109 dynes/cm2 with most of the monomers here employed.

SynopsisWater-ethanol permselective membranes were prepared through plasma graft polymerization of acrylic acid, methacrylic acid, and acrylamide onto porous polypropylene film. In these membranes, the functions of permseparation and mechanical properties are shared respectively to the graft polymer layer and the substrate f i l m . Higher permselectivity of water is achieved with the ionization of the acrylic acid and the methacrylic acid-grafted membranes. Permselectivity is dependent on the degree of grafting, and it is necessary to fill the pores of substrate film with graft polymers. Permseparation of water was investigated with respect to the feed ethanol concentration and also to the temperature dependence.Thus, the construction of membranes with more hydrophilicity seems to be more preferable for water permseparation. However, too much hydrophilicity often leads to the dissolution of the membrane in contact to the aqueous feed solutions. To avoid such defects, membranes are usually modified, for example by crosslinking.A useful procedure to obtain the insoluble membranes lies in graft polymerization of hydrophilic monomers onto stable substrate film. Very hydrophilic layers, which should be soluble in the homopolymer state in the feed solution

Some biodegradable polymers of as poly(y-lactone) and poly(succinate) were surface-treated by glow discharge plasmas under an appropriate condition, and the effects were investigated with respect to the weight loss, surface morphology change, and bio-degradation. The weight loss rates by oxidative plasmas were in general higher than those for a polyester sheet made of poly (ethylene terephthalate). After glow discharge treatments, the characteristic surface morphology appeared by the observation of scanning electron microscopy (SEM). Surface became more wettable, and activated by plasma treatments. Bio-degradation of these polymers was investigated in composts under appropriate condition, and the effects were discussed.

-, T~ukuba, T~u k u b~~. ,Ibaraki 305-8565, JapanSurface treatments using glow discharge plasmas from 0, and Ar were applied to blend sheets of poly(E-capro1actone)-polycarbonate (PCL/PC), which had been produced by extrusion from melts of the mixture at various blend ratios. As to the reactivity of these two plasmas, 0,-plasma forms the oxidative species to be reactive in general, while Ar-plasma is non-oxidative. Weight loss by the oxidative 0,-plasma etching increased with the content of PCL in the polymer blends. The surface became hydrophilic by plasma treatment, and the changes were affected also by the blend ratio. PC and the PC-rich blend sheets became more hydrophilic than the PCGrich blends after plasma treatments. The 0,-plasma treatments were more effective than non-oxidative Ar-plasma treatment in increasing the hydrophilicity. Hydrophilic change was related to the increase in the polar contribution of surface energy. Plasma TreatmentsPlasma for surface treatments was generated by inductively coupled discharge at 13.56 M H z using an RF generator (HFS 005, Nihon Koshuha Co. Ltd., Japan). Polymer blend sheets were treated by plasmas from 0, and Ar in a reactor made of Pyrex glass tubing (4.4 cm diameter, 26 cm length) (14). Gas supply for glow discharge was regulated by the opening of the v&e (=-4BMG, Nupro CO., USA), and the system presswe 270, B-tron Co., USA).