Copolymerization of polar and non-polar monomers: free radical polymerization and late transition metal catalyzed insertion polymerization

Open Access
Author:
Luo, Rong
Graduate Program:
Chemistry
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
September 16, 2008
Committee Members:
  • Ayusman Sen, Committee Chair
  • Harry R Allcock, Committee Member
  • John V Badding, Committee Member
  • T C Mike Chung, Committee Member
Keywords:
  • 1-alkenes
  • copolymerization
  • acrylates
Abstract:
The addition of the heterogeneous Lewis acid, acidic alumina (Acidic, Brockmann I, standard grade, ~ 150 mesh, pH = 4.5±0.5 in aqueous solution) to the 2, 2’-azobis (2-methylpropionitrile) (AIBN) -initiated copolymerization of methyl acrylate (MA) with 1-alkenes results in significant increase in polymerization rate and increased incorporation of the later monomer to the polymer backbone. Alumina can be recovered by filtration and reused repeatedly with no loss of activity. This led to the design of an Al2O3-filled column reactor system for the copolymerization reaction The addition of insoluble acidic alumina to controlled radical NMP and RAFT polymerizations of acrylate monomers results in significantly higher reaction rates and conversions. The effect is particularly dramatic since only a small fraction of the Lewis acid sites that are present on the alumina surface can actually interact with the acrylate. The Lewis acid-enhanced polymerizations have “living” characteristics, allowing the synthesis of block copolymers. The alumina can be quantitatively removed by filtration and recycled with no significant loss in efficacy. The addition of both homogeneous and heterogeneous Brønsted acids resulted in increased monomer conversion and 1-alkene incorporation. Further, the heterogeneous Brønsted acids can be recycled without loss of activity. A direct correlation exists between the ability of the Lewis or Brønsted acid to bind to the ester group of the acrylate/methacrylate monomer and its ability to promote the copolymerization reaction. For Lewis acids, there is also a direct correlation between the charge/size ratio at the metal center and their ability to promote copolymerizations. The first electron transfer induced iron-catalyzed atom transfer radical polymerization (ATRP) system for styrene derivatives was developed. Environmental benign reducing agents tin(II) 2-ethylhexanoate (Sn(EH)2) and D-glucose were employed to constantly regenerate active Fe(II) species. This reducing/reactivating cycle allowed the controlled polymerization even in the presence of a limited amount of air. Furthermore, the amount of iron catalyst could be reduced to as low as 0.01 mmol while retaining sufficient control over the polymerization. Monomers with electron-withdrawing substituents polymerized faster than those having electron-donating substituents. Block copolymers were obtained by chain extension of polystyrene macroinitiators. Well-defined copolymers of styrene and methyl methacrylate (MMA) were also synthesized using this iron-based catalyst, and the MMA content in the copolymers could be varied by changing the monomer feed ratio. The palladium-catalyzed alternating copolymerization of ethene and carbon monoxide has been extensively studied in the last two decades. A series of polyketones with very low CO content has been synthesized using palladium catalyst bearing (P-SO3-) ligand by varying the monomer feed ratio and reaction conditions. We have also demonstrated that the reason for the non-alternation in this system is more complicated than just the instability of the five-membered chelate resting state existed in the catalytic cycle, and the less dramatic difference in CO and ethene binding affinity also plays an important role for this non-alternating fashion. The kinetics and thermodynamic data has allowed us to estimate the fraction of non-alternation due to double ethene insertion during the copolymerization.