ATRP LabDAHLIA - Preparation of Poly(n-Butyl Acrylate-b...

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Preparation of Poly (n-Butyl Acrylate)-b- Poly (styrene) via Atom Transfer Radical Polymerization (ATRP)Dahlia NingrumCHEM 548February 28, 2012
Abstract: The purpose of this experiment was to copolymerize n-butyl acrylate with styrene via atom transfer radical polymerization (ATRP). Poly(n-butyl acrylate) was successfully polymerized by ATRP with a 21% recovery. The resulting polymer had a Mnof approximately 3200 g/mol as determined by both 1H NMR analysis and GPC data with a PDI of 1.5856. This polymer was then used as a macroinitator to polymerize poly(styrene) via ATRP as well, resulting in a 32% recovery. 1H NMR analysis found that the resulting polymer had a Mnof 7170 g/mol, while GPC analysis resulted in a Mnof 10839 g/mol with a PDI of 1.5736. Regardless of the difference in Mnvalues, this data shows that the copolymerization of p(nBA) with p(St) was successful.Introduction: Atom transfer radical polymerization (ATRP) is a controlled radical polymerization technique that combines versatility of free radical polymerization with the control of living polymerization. The key controlled synthesis of block copolymer is to limit termination and side reaction, maintain high chain end functionality, and avoid slow initiation.2 Termination can not be completely avoided because of the nature of polymerization process but it can be minimized through the careful selection of the reaction condition and adjustment of the equilibrium between active and deactive species.2When the dormant, or inactive, species is preferred, side reactions, such as redox of the radicals and carbon-meta bonding, are less likely to occur.3Equilibrium can be adjusted through the addition of a metal catalyst such as copper (I) and cooper (II). Cooper (I) activates or “wakes up” polymer chains while copper (II) deactivates or “put to sleep” the active polymer chains. Adding different amount of these species dictates the rate that polymer chain fluctuate between active and deactive species. Reaction rates can be suppressed by the addition of CuBr2due to Le Chatelier's principle. A copper (II) species was not added to the reaction solution for step to make copolymer, because the ideal equilibrium between the active and deactive species and ideal rate of the reaction could be reached without it. PMDETA is a ligand that makes it possible for the metal catalyst to be dissolved into the reaction solution. The ligand also provides selectivity in the polymerization through steric interactions between growing polymer chain, the ligand and the monomer. Choice of initiator and the order of block synthesis play a large role in the polymerization. An initiator was chosen to match the monomer.3The first monomer polymerized

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