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Atom Transfer Radical Polymerization of Acryl Amide in Reverse Suspension

Shirazi Amin, Alireza | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41878 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Pourjavadi, Ali
  7. Abstract:
  8. Atom transfer radical polymerization (ATRP) is a convenient approach to synthesis of polymer with narrow molecular weight distribution. ATRP of acrylamide (AAm) is taken into consideration because of the intrinsic properties of acrylamide such as water solubility and biocompatibility. As reported in many recent works, polymerization of acrylamide by this method didn’t provide monomodal molecular weight distributions. In best condition with strong ligands such as Me4Cyclam, polymerization was carried out in a short time with high yield but polymerization was not highly controlled. It was shown that polymerization of acrylamide under typical ATRP condition displayed a much lower ATRP equilibrium constant than the the other common monomers. Whereas the most popular advantageous of ATRP in comparison with the other polymerization process is in representing low polydispersity index, so modification of ATRP conditions to achieve low PDI for Poly(AAm) is still a challenging subject. In this following work optimization of ATRP condition for polymerization of acrylamide was attempted to control polydispersity index of Poly (AAm). Atom transfer radical polymerization (ATRP) of acrylamide (AAm) was carried out in water - tolouene (1: 2 v/v) mixture in reverse suspension at room temperature. Chloroacetonitrile and CuCl/pentamethyldiethylenetriamine (PMDETA) complex were used as water soluble initiator and catalyst respectively. The additional amount of CuCl2 (50% moles of CuCl) was used in order to reduce the polydispersity index (PDI) of poly (AAm) through decreasing the amout of activated specious. According to poly (AAm) nature, it is well known that polymerization of AAm through ATRP cannot proceed in a very good manner (low PDI). The inactivation of the catalyst by complexation of copper by the forming polymer (copmplexation with amide functionality) is the side reaction which inhibits the polymerization process to have low PDI. As a result of that, accomplishment the polymerization of AAm by ATRP in reverse suspension reduces the rate of polymerization but also can reduce polydispersity index of poly (AAm). The temperature of process in which the polymerization was occurred is also has significant effect in rate of polymerization, degree of conversion and polydispersity index of poly (AAm). ATRP of acrylamide was carried out in different temperature. Best result was achieved at room tempreture. Increasing the temperature resulted in increasing the polydispersity index of poly (AAm) too. At the higher temperature GPC traces show shoulder and and as a result of that PDI was raised considerably. Low temperature and reverse suspension provided conditions through which ATRP of acrylamide proceeded with low PDI and monomodal molecular weight distribution was achievable. Although high molecular weight of polymer was not obtainable through this method but relatively low polydispersity index could be its advantageous. The choice of appropriate reverse suspension with special polarity is also important for the design of well-controlled ATRP system. Even though the ATRP of acrylamide is not controlled process as it reported in many recent paper, by using the reverse suspension system at low temperature, poly(AAm) with molecular weight about Mn= 113600 g/mol and Mn/Mw=1.06 was synthesized. The living moiety of resulted polymer by atom transfer radical polymerization in reverse suspension was also proved by using this polymer as a macroinitiator in a new polymerization process. The prepared polymer through this reaction showed molecular weight about Mn = 8576000 g/mol and Mn/Mw = 1.14
  9. Keywords:
  10. Acryle Amide ; Suspension Polimerization ; Atom Transfer Radical Polymerization

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