In this paper we show that hyperbranched polymers can be used as a host matrix for electrostatic entrapment of enzymes. Specifically, amine-functionalized glucose oxidase (GOx+) and horseradish peroxidase, as well as poly(amidoamine) dendrimer-modified horseradish peroxidase, reversibly sorb into polyanionic, hyperbranched poly(sodium acrylate) (PAA-) films that are on the order of a few hundred angstroms thick. The quantity of GOx+ entrapped within the PAA- films depends on the nature of film preparation but is typically on the order of 0.06 unit/cm2. The extent to which entrapped GOx+ retains its activity depends on the film history, but for PAA-/GOx+ composites not exposed to glucose and stored at 4 degrees C, the original activity is retained for up to 68 days and perhaps longer.

A new method to prepare functional grafts on polyethylene is described. In this chemistry, a terminally functionalized poly(tert-butyl acrylate) is first attached to an oxidized polyethylene film. Subsequent hydrolysis of the tert-butyl esters at room temperature then produces a film with some poly-(acrylic acid) grafts. Although this initial graft is present at low density, repetition of this process through 2-4 more cycles produces a heavily grafted polyethylene that exhibits much of the same chemistry seen for hyperbranched poly(acrylic acid) grafts on more defined inorganic surfaces. The resulting grafts are more effective platforms for further ionic modification of polyethylene than simple oxidized polyethylene.

A combination of in situ and ex situ ellipsometric studies and infrared spectroscopy was used to evaluate the extent of solvation of a thin covalently assembled, hyperbranched poly(acrylic acid) (PAA) graft on a gold substrate. The results show that these thin films swell reversibly by up to 300% upon immersion in a pH 1.7 buffer and by more than 500% at pH 10.7. This change in thickness, which is centered at pH 4.3, results from acid-group ionization. Covalent modification of the PAA thin films can be used to control both the extent of film swelling and the pH range over which the films undergo protonation/deprotonation reactions. For example, partial fluoramidation of the PAA carboxyl groups raises the pH where ionization occurs to 6.7 and reduces the extent of swelling (compared to the dry film) to 130% and 150% at pH 1.7 and 10.7, respectively. Solvated poly(sodium acrylate) films also serve as polyvalent ion-exchange substrates for immobilization of polyvalent cations including dendrimers, poly-L-lysine, and poly(allylamine). This immobilization technique yields self-assembled nanocomposites of the polyanionic surface graft with polycationic guests. pH modulation allows the guests to be released.

Ion‐exchange polymers with “on”/“off” solubility can be prepared from N‐isopropylacrylamide (PNIPAM) copolymers that incorporate hydroxamic acid ligands. Such complexing agents quantitatively remove trace amounts of FeIII from aqueous solutions (vial 1) by precipitating the metal – polymer complex on heating (suspension in vial 2). Physical separation of the insoluble polymer leaves a metal‐free solution (vial 3). Similar fluorous phase‐soluble hydroxamic acid derivatives of fluoroacrylate polymers remove FeIII ions from organic solutions by liquid/liquid phase separation.

Hyperbranched poly(acrylic acid) and poly(N-isopropylacrylamide) grafts on gold and polyethylene films are good substrates for a new, mild hydrogen-bond-based grafting method. In this chemistry, a hydrogen-bond-donating or -accepting hyperbranched graft couples to a polymeric acceptor or donor in ethanol solution through multiple hydrogen-bonds. In contrast to plain surface-functionalized polyethylene films or to functional monolayers on gold, hyperbranched grafts are more capacious and more tenacious in this hydrogen-bond graft chemistry. Substantial amounts of polyacrylamide or poly-(acrylic acid) reversibly bind to the hyperbranched graft based on IR spectroscopy, fluorescence spectroscopy, and ellipsometry. Fluorescence studies using dansyl-labeled soluble polymers that were hydrogenbonded to hyperbranched grafts show that these hydrogen-bond assemblies are stable to prolonged extraction with protic and aprotic solvents. These interfacial hydrogen-bonded assemblies do not readily disassemble unless the hydrogen-bond donor is deprotonated with base.