Chemistry in adsorbed monolayers. 2. Thermal and photochemical grafting reactions at the polymer-filler interface

Abstract

The photochemistry of adsorbed long-chain a-diazo ketones, azidoformates, and a-azido ketones was explored as a method of improving the adhesion between polyethylene and polar inorganic fillers. A GC-MS study of the photoreactions of monolayers of intermediate chain length compounds adsorbed on alumina established that grafting reactions predominated and that cyclization and interchain reactions were much less pronounced than analogous photoreactions in cyclohexane solution. This result was attributed to the decreased mobility of the surface-active compounds at the interface. The effects of surface modification of alumina and silica gel of large particle size and fumed silica of 17-20-nm particle size on the tensile properties of blends with linear low-density polyethylene were investigated. Monofunctional grafting agents such as octadecanoyl azide resulted in no improvement in elongation at break in comparison to untreated filler, a result indicating that simple wetting of the filler surface was insufficient to promote adhesion between polymer and filler in this system. With bifunctional grafting agents containing both a photochemically and a thermally active group, such as 12-azido-l-diazo-2dodecanone and l-diazo-ll-dodecen-2-one, significant improvements in elongation at break were observed over the untreated filler. Evidence for improved adhesion between polymer and surface-modified filler was provided by scanning electron microscopy of fracture surfaces.

Bifunctional coupling agents for improved mechanical properties in fiberglass/polyethylene composites

“…18 The effect of heat on the decomposition of the diazoketone group over a range of temperatures was determined by depositing samples of A and B onto IR disks, heating the coated disks for various times at a prescribed temperature, and measuring the FTIR spectra on the cooled disks. NMR and FTIR studies at 150°C were undertaken by depositing these compounds onto watch glasses from solutions in CHCl 3 , and heating them in an oven controlled at this temperature.…”

“…In the early 1990s Holden et al 18,19 synthesized and tested a series of bifunctional compounds containing diazoketone, azide, and alkene functional groups. Several compounds in this series containing the diazoketone group were able to react with the hydroxylated surfaces of alumina and silica gel.…”

Quantum Yield Values for the Decomposition of Several Surface‐active Photoreactive Amphiphiles

“…The five compounds studied (1-5) were synthesized as described by McGarvey and Holden (1990). For the quantum yield determination of 12-azido-1-diazo-2-dodecanone (l), l-diazo-17-octadecen-2-one (2) and l-diazo-ll-dodecen-2-one (3) irradiation was carried out using an optical bench system.…”

“…Despite the apparent utility of these surfaceactive photoreactive compounds for biological and other uses, quantum yield values for the decomposition of long-chain fatty acid derived a-diazoketones, acyl azides and azidoformates are unavailable. Our interest in these compounds was based on their utility as surface-modifying agents for hydroxyl-bearing surfaces, whereby the amphiphiles self-assembled on hydrophilic substrates and were subsequently grafted to the support by UV irradiation (Holden et al, 1987;McGarvey and Holden, 1990). In order to determine the efficiency of the surface photografting reaction, quantum yield measurements for the photodecomposition of several selected compounds were performed in hexane solution.…”

Gas‐phase photoinduced graft polymerization of acrylic acid onto polyacrylonitrile ultrafiltration membranes

“…Membrane samples were placed in the center of a thermostatable reaction chamber (diameter: 100 mm) with gas entrance and exits, equipped with either a glass or a quartz window ( Figure 1 Experimental setup for gas phase photo graft polymerization onto membranes: 1) Illumination system, including UV lamp HBO 350, quartz mirrors, and collimating lens; 2) reactor light entrance window (glass or quartz, exchangeable); 3) membrane sample; 4) gas supply from nitrogen tank; 5) flow meter; 6) thermostat; 7) temperature-controlled monomer reservoir; 8) temperature-controlled reactor; 9) exiting monomer sorption bottle.…”