and growth of the metal nanoclusters preferentially occur. Consequently, the size of the resulting nanoparticles matches the dimension of the nanometer-sized cavities inside these swollen domains. The possibility of controlling the growth of the metal nanoclusters by changing the morphological features of the support represents a unique feature of resin supports, in which the metal nanoparticles are generated inside the swollen polymer network and not simply at its surface. It can be inferred that functional resins characterized by a narrower distribution of nanoporous domains will make it possible to control even more precisely the size and size distribution of the metal nanoclusters generated inside them, a task that we are going to turn to in the near future.
Experimental
Solvents and chemicals were of reagent grade and were used as received. XRM analyses were obtained with a Cambridge Stereoscan 250 EDX PW 9800 apparatus. TEM micrographs were obtained using a Philips CM100 microscope. ISEC measurements were carried out using an established procedure and a standard chromatographic set-up described elsewhere [13,14]. The ESR spectra were recorded on an X-band JEOL JES-RE1X apparatus at 9.2 GHz (modulation 100 kHz). Details of sample preparation and measurement have been reported elsewhere [18].
Resin Preparation: Monomers were mixed in the desired ratios and the resulting mixtures (10 g) were diluted with 5ยฑ10 % w/w dimethylformamide in order to ensure complete miscibility. They were exposed to the c-rays from a 60 Co source at 0.5 Gy s ยฑ1 at room temperature and at a distance of 21 cm for 72 h. The resulting clear transparent rods were crushed, extensively washed with methanol, acetone, and diethylether, vacuum dried, and sieved to a particle size <0.18 mm.
Impregnation with Pd: Resin (2 g) was added to a solution of 44 mg Pd(OAc) 2 (1 % by weight of Pd with respect to the polymer) in 50 mL tetrahydrofuran (THF)/water 4/1. The suspension was stirred overnight, then the resin was filtered off, washed thoroughly with THF and diethylether and allowed to dry in air.
Pd Reduction: Exchanged resin (1 g) was swollen in ethanol (20 mL) for 1 h. A solution of NaBH 4 (0.14 g) in ethanol (40 mL) was added and the resulting suspension stirred overnight. The resin was filtered off, washed with ethanol and THF, and dried under vacuum at room temperature to constant weight.