Factors affecting the properties and behaviour of blockcopolymer micelles

Abstract: Polymers are of fundamental importance to our society and can befound in many different products. Block copolymers are polymerswhich are divided up into distinct blocks of two or more differentmonomers. Block copolymers with regions of difference in polarityare capable of self assembling into ordered systems. These systemscan be tailored to be used for different purposes such as templatesfor material synthesis or drug delivery vehicles. The objective ofthis study was to investigate how different methods of preparing asample affect the micellar structures for the systems poly(2-ethylhexyl methacrylate) (PEHMA) - quaternized poly(dimethylaminoethyl methacrylate) (qPDMAEMA) and poly(2-ethyl-hexylmethacrylate) (PEHMA)- poly(methacrylic acid)(PMAA). The parametersstudied were choice of cosolvent and order of mixing, i.e. mixingwater with polymer solution or polymer solution with water. Thestability over time of the micellar structures were studied as wellas the Zetapotential and adsorption to model silica surfaces. Theresults showed that using different cosolvents yielded a differencein size but not in micelle stability over time. The investigationalso showed that preparing the sample by adding polymer solution towater, versus adding water to polymer solution, yielded nosignificant difference in polymer size or stability. However as thestudy was done in small volumes the concentration gradient producedduring the two methods may not differ that much and using largersample volumes may produce different results. Using a triblockcopolymer over a diblock copolymer of a corresponding size yieldedvastly different results in size, stability and adsorption. Thetriblock polymer produced smaller more stable aggregates whichadsorbed quickly and the diblock copolymer produced large,polydisperse aggregates which started to aggregate after around 7days and adsorbed slowly.