Scaling Properties of two-dimensional Star-branched Polymers grown by Diffusion
- PDF / 216,698 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 33 Downloads / 131 Views
0947-A03-48
Scaling Properties of two-dimensional Star-branched Polymers grown by Diffusion Guillermo Ramirez-Santiago1, and Carlos I. Mendoza2 1 Depto. de Fisica-Quimica, Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Po Box 20-364, Mexico 01000 D. F., Mexico, 04010, Mexico 2 Depto. de Polimeros, Instituto de Investigacion en Materiales, Universidad Nacional Autonoma de Mexico, PO Box 70-360, Mexico D.F., Mexico, 04510, Mexico
ABSTRACT We present an off-lattice numerical algorithm based upon pure diffusion to construct twodimensional star-branched polymers with one, three, six and twelve branches. We built up structures with a total of up to 30,000 monomer units. For each one of them averages over one hundred independent configurations were taken. From a finite size analysis the scaling properties of the pair correlation function as well as the radius of gyration were obtained. Our findings indicate that the fractal dimension of the structures are: df=1.21 (0.03) for a linear polymer, df==1.21(0.02), for three branches, df==1.23 (0.02) for six branches and df=1.26 (0.03) for twelve branches. INTRODUCTION Star branched polymers are materials with many fascinating properties. They play an important role in different chemical and physical polymerization processes. Due to their well-defined molecular architecture these systems can be regarded as models with soft and ultra-soft inter-particle interactions. Since they interpolate in between hard colloids with strong repulsive core on one side, and as soft and flexible polymeric systems, on the other, they are relevant as soft condensed matter system. Hence, they are ideally suited for proving fundamental theories for the description of the structure-property relationship. Since the prediction and interpretation of the conformational properties of branched polymers is difficult, numerical simulations are very useful to obtain a better understanding of structural and conformational properties of these systems. A number of algorithms based upon on-lattice diffusion [1] or kinetic processes [2,3] have been developed to describe the irreversible growth of linear polymers. Some of them have the property of producing polymers that grow indefinitely [3] without forming cages. That is, they mimic the conformation of polymer chains in the good solvent limit. In this report we introduce a different algorithm based upon a pure off-lattice diffusive process. The model produces branched polymer structures and allows conformations in which one or more branches may end up confined (trapped) in which case the process terminates. Due to the directed processes used to growth the branched structures the algorithm is less sensitive to attrition than a self-avoiding walker. We have built up two-dimensional star-branched polymers with one, three, six and twelve branches. An analysis of the structure and the conformation yielded the following fractal dimensions: df=1.21 (0.03) for a linear polymer, df==1.21(0.02), for three branches, df==1.23 (0.02) for six branches and df=1.26
Data Loading...
