Experimental Studies of Cluster-Size Distributions During   Colloidal Aggregation
{'Code': '03090006', 'Directorate': {'LongName': 'Direct For Mathematical & Physical Scien'}, 'Division': {'LongName': 'Division Of Chemistry'}}
{'SignBlockName': 'Claudia Thomas'}
This project is in the general area of analytical and surface                   chemistry and in the subfield of colloidal aggregation.  This                   research continues the Principal Investigator's application of                  optical particle size pulse analysis to characterize the kinetics               of colloidal aggregation processes and the structure of                         aggregates formed under different conditions.  This method permits              direct testing of the fundamental theories of colloid                           flocculation.  Two model systems will be studied systematically:                1) salt-induced coagulation of colloidal polystyrene microspheres;              2) antigen-antibody agglutination reactions.  Temporal evolution                of the cluster-size distribution will be recorded as a function of              such factors as ionic strength and pH of the electrolyte solution               in order to test theories of irreversible aggregation.  The                     particle size analyzer will be improved to enable analysis of                   smaller particles than currently possible.  In addition, light                  will be collected not only at small angles but also at a range of               larger scattering angles.  This will enable determination not only              of the mass but also the radius of gyration and hence the fractal               dimensionality of the clusters.  The relation of cluster structure              to cluster growth and cluster-size distribution will be                         characterized.                                                                                                                                                  The aggregation of small particles to form larger structures is of              major importance in such diverse areas as air and water pollution,              materials processing, catalysis, medicine and biology.  Both                    experimental and theoretical studies are necessary to advance our               understanding of colloidal aggregation.  Optical particle size                  pulse analysis enables direct measurement of the particle size                  distribution and temporal evolution, and direct testing of the                  fundamental theories of cluster growth.
{'FirstName': 'Richard', 'LastName': 'Cohen', 'EmailAddress': 'rjcohen@mit.edu', 'StartDate': '07/01/1988', 'EndDate': None, 'RoleCode': 'Principal Investigator'}
{'Name': 'Massachusetts Institute of Technology', 'CityName': 'Cambridge', 'ZipCode': '021394301', 'PhoneNumber': '6172531000', 'StreetAddress': '77 MASSACHUSETTS AVE', 'CountryName': 'United States', 'StateName': 'Massachusetts', 'StateCode': 'MA'}
{'Code': '1972', 'Text': 'ELECTROCHEMISTRY & SURFACE CHE'}
{'url': 'https://www.nsf.gov/awardsearch/download?DownloadFileName=1987&All=true', 'xml': '8720308.xml'}