The reverse osmosis properties of asymmetric membranes prepared from a novel class of aromatic polyamides and polyamide-hydrazides are described. These materials are characterized by their unusually high degree of selectivity to dissolved salts (ca. >99.4% rejection) at moderately high levels of flux in the range 1 < .A (gal ft-2 day-1) < 30, with excellent chemical stability and mechanical properties. The membranes are similar in structure to that reported for cellulose acetate, i.e., they contain a thin dense surface layer supported on a porous matrix.

synopsisThe dissolution temperature of the crystalline platelets of polyacrylonitrile in propylene carbonate bears a linear relationship with the crystallization temperature T,. The step heights 5 of the crystalline platelets measured by electron microscopy increase with increase in crystallization temperature, in accordance with the current theory of high polymer crystallization in dilute solution. The step heights were found to be 100, 130, and 150 A. for T, of 95, 116, and 125OC., respectively. By extrapolating the experimental values of T, to the value a t 5 = m, a characteristic constant (T,,,)= is obtained. The (T,,,)-was 175°C. for the sample studied in propylene carbonate.The interfacial free energy, u., calculated from the melting point and the step height is of the order of 1950 cal./mole of emerging chain repeat unit, or 45 ergs/cm.2 as compared to 1900 cal./mole or 70 ergs/cm.* for polyethylene. It appears that the surface free energies of various organic polymers are remarkably similar. Although the degree of crystalline perfection of polyacrylonitrile is inferior to that of organic crystals with threedimensional order, polyacrylonitrile displays a crystallization behavior similar to other semicrystalline polymers; this conclusion is supported by the linear relationship between T, and T,, the variation of the step height with the crystallization temperature, and the sigmoid relationship of the fractional change in specific volume as a function of time during crystallization.

Poly(hydroxystyrene) (PHS) reacts with norbornene in the presence of acid to form a phenoxynorbornane pendent group through the hydroalkoxylation of the norbornene double bond by the phenol −OH group of PHS. Films of PHS, an aqueous base soluble polymer, containing norbornene derivatives and a photoacid generator (PAG) create a negative tone photopatternable composition. Acid generated in the exposed regions of the film promotes the hydroalkoxylation reaction generating the phenoxynorbornane pendent group, rendering the film insoluble in an aqueous base developer. Both dinorbornene and mononorbornene-functional additives were evaluated. In the case of the mononorbornene additive, a unique example of a negative tone photopatterned film that can be reworked after patterning by dissolution in a mild solvent at room temperature was demonstrated. Polymers containing aliphatic alcohol and carboxylic acid pendant functionalities could be photopatterned in the presence of dinorbornene additives showing the generality of this method.

Thermograms of reaction products of cellulose with dimethylolurea (DMU) or dimethylolethyleneurea (DMEU) homopolymers show the peak associated with cellulose decomposition is shifted up by as much as 20°C. Solubility measurements in cupriethylenediamine (Cuene) indicate the homopolymers are present as side groups on the cellulose. Cellulose reacted with DMU or its homopolymer is only insoluble in Cuene when oxymethylene crosslinks are simultaneously formed by CH2O. These crosslinks do not affect the thermal stability of cellulose. Linkages to DMEU or its homopolymer are relatively stable to alkaline hydrolysis and may be distinguished from oxymethylene linkages by comparison of thermograms and solubilities before and after acid hydrolysis. Comparison of thermograms of cellulose with those of the n‐methylol compounds, their homopolymers, physical mixtures of cellulose and the homopolymers, and reaction products of cellulose with DMU, DMEU, and CH2O, demonstrated that, depending upon the reaction conditions, CH2O evolution, in situ homopolymenzation, cellulose crosslinking by CH2O, by the n‐methylol compounds, and reaction with their oligomers may occur. Reaction variables, viz., pH, temperature, nature and concentration of catalyst, the time‐temperature interval between application of the n‐methylol compound and the final reaction, and the type of n‐methylol compound determine which reaction predominates. The modification of cellulose by DMU shows a greater dependence on catalyst type than does DMEU which readily polymerizes to low molecular‐weight products and evolves CH2O which crosslinks the cellulose.

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