Antithrombogenic properties of non-ionic polymers

Human serum albumin and γ‐globulin form complexes with various synthetic polymers through some secondary binding forces. This complex formation between serum proteins and ionic or nonionic polymers is discussed. Polycations and polyanions interact with serum proteins through electrostatic interaction force mainly. There is strong pH dependence on the interaction, because these proteins show amphoteric properties. When ionic polymers interact strongly with proteins, the conformations of both proteins are changed by the complexation. In case of complexation with nonionic polymers, γ‐globulin tends to be precipitated at higher pH than 6. In addition, there exists suitable hydrophobicity of nonionic polymers for complex formation with high efficiency. On the contrary, albumin is easily precipitated by nonionic polymers in the lower pH region. There are little conformational changes of proteins through complexation with nonionic polymers except for the case of poly(N‐vinyl‐2‐pyrrolidone) treatment. Selective complexation is achieved by some nonionic polymers having less hydrophobicity such as poly(ethylene oxide). High efficiency of selective complexation is observed by control of the pH and the hydrophobic properties of the noionic polymers.

The usage of aqueous lubricants in eco-friendly bio-medical friction systems has attracted significant attention. Several bottle-brush polymers with generally ionic functional groups have been developed based on the structure of biological lubricant lubricin. However, hydrophilic nonionic brush polymers have attracted less attention, especially in terms of wear properties. We developed bottle-brush polymers (BP) using hydrophilic 2-hydroxyethyl methacrylate (HEMA), a highly biocompatible yet nonionic molecule. The lubrication properties of polymer films were analyzed in an aqueous state using a ball-on-disk, which revealed that BPHEMA showed a lower aqueous friction coefficient than linear poly(HEMA), even lower than hyaluronic acid (HA) and polyvinyl alcohol (PVA), which are widely used as lubricating polymers. Significantly, we discovered that the combination of HA, PVA, and BPHEMA is demonstrated to be essential in influencing the surface wear properties; the ratio of 1 : 2 (HA : BPHEMA) had the maximum wear resistance, despite a slight increase in the aqueous friction coefficient.

The first part of this paper describes cationic polymerizations of cyclic imino ethers, 2‐oxazolines and 5,6‐dihydro–4H–1,3–oxazines, which proceed via cyclic onium propagating species or via covalently bonded alkyl halide species. In an extreme case, both ionic and covalent species are present in equilibrium and propagate concurrently. The propagation rate constants due to the respective species were determined. A poly(cyclic imino ether) becomes hydrophilic or lipophilic dependent on the substituent of the monomer. Based on this principle, various types of nonionic polymer surfactants have been prepared, e.g., diblock and triblock copolymers, graft copolymers, and surfactants having one 2‐oxazoline chain. The second part is concerned with ring‐opening polymerizations of new eight cyclic trivalent phosphorus monomers. These polymerizations produced phosphorus‐containing functional polymers such as a chelating resin. 31P NMR analyses of polymerization of cyclic phosphinite monomers led to propose a new mechanism of “Electrophilic Ring‐Opening Polymerization”.

A polymer-mediated paramagnetic spin relaxation (PSR) filter is presented for the selective suppression of signals from polymer-interacting species in the 1D and 2D NMR spectra of mixtures. The combined use of Gd3+ and a polymer with a high transverse relaxation enhancement (R2p , which gives a measure of the Gd3+ -complexing ability) results in the suppression of signals from any polymer-interacting component in mixtures, irrespective of their R2p . By using poly(acrylic acid) (PAA) as a model system, we demonstrate selective filtering of the signals of typical low-R2p species (insensitive to Gd3+ ), such as molecular/polymeric cations and non-ionic polymers, which, through PAA recognition (electrostatic/hydrogen-bonding interactions), become exposed to the paramagnetic effect of Gd3+ , while leaving non-PAA-interacting species unaffected. Typical suppression conditions involve PAA (approximately equimolar amount with respect to the species to be filtered) accompanied by sub-mm concentrations of Gd3+ and T2 -filters ≤100 ms. Overall, by exploiting the PSR principles and the recognition properties of polymers, selective NMR filtrations that are not attainable by diffusion, relaxation, or direct PSR filters, can be achieved.

Copolymers containing amino groups are useful in diverse fields such as ion exchange, flocculation, paper stock treatment, and synthetic fibers. While investigating methods for producing such polymers, the authors found that certain diallyl compounds gave soluble copolymers rather than the anticipated gels. This article discusses the relationship of monomer structure to polymer properties, confirming and extending the preceding publications by Butler and others (2-7, 9, 70). Some applications of soluble copolymers are described. When diallyldimethylammonium chloride was copolymerized with acrylonitrile or with acrylamide, the copolymer contained substantial amounts of quaternary compound, yet dissolved in a suitable liquid with no trace of gel. Table I provides examples of this behavior, listing a series of acrylamide copolymers prepared by redox polymerization in water. Solution viscosities were high, indicating molecular weight of the order of one million. Analysis of the copolymers showed that substantial amounts of quaternary compound had been incorporated but without appearance of pendant double bonds. Some of these copolymers were tested as strengthening agents for paper. Paper fibers in aqueous suspensions develop a negative charge; hence, cationic materials, particularly polycationic polymers, tend to be irreversibly adsorbed at the fiber surface. Nonionic or anionic polymers are not adsorbed to the same extent unless mordants such as alum are used. Paper is made from very dilute slurries (0.1 to 0.6y0 on paper machines, 0.0357, on laboratory equipment), so the adsorption mechanism must be efficient for economic utilization of chemical additives to the fiber slurry. These copolymers do improve the strength of paper substantially (Table 11). Other results not listed show that the polymers are effective over a wide p H range. Table I1 also shows that the products are true copolymers. Paper stock slurries were treated with a solution containing 10% polyacrylamide and 27 , monomeric diallyldimethylammonium chloride. Physical properties of the haiidsheets were not improved, indicating that polymer must contain chemically bonded cationic groups to be effective. Copolymers of the same allyl monomer with acrylonitrile are listed at the top of Table 111. Nitrogen analyses showed that the copolymers contained about one half as much allyl compound as was present in the monomer charge. The presence of basic sites was confirmed by a dye adsorption test. Copolymers were of fairly high molecular weight (roughly 100,000 to 300,000 range), but were soluble in dimethylformamide and in aqueous sodium thiocyanate. The 87-13 copolymer was spun successfully into fibers. In this instance an approximately 107, polymer solution in 50% sodium thiocyanate was extruded through a spinnerette into water at a b o g 0 C. The fiber was washed, stretched, and dried. It had typical properties for an acrylic fiber. Experiments with other allyl compounds, also listed in Table 111, show that the ability to form high molecular weight, soluble copolymers is a general property of diallyl compounds of this class. O n the other hand, if three or four allyl groups were attached to nitrogen, the products gave gels in dimethylformamide and were presumably cross-linked. A sulfur compound also gave a soluble copolymer. N,N-Diallylmelamine is a monomer that can lead to soluble or to insoluble copolymers depending on the reaction condi-