Polystyrene‐block‐poly(methyl methacrylate): Initiation Issues with Block Copolymer Formation Using ARGET ATRP

Abstract

The synthesis, kinetics, and characterization of polystyrene and poly(methyl methacrylate) block copolymers produced by ARGET ATRP are discussed. Halogen exchange is used and the polymerization appears to be living in the generation of the second block. On further investigation, the GPC traces exhibit a shoulder, which suggests poor initiation of the macroinitiator. Previous reports suggest that to increase the initiation effi ciency of the second block, 10% styrene monomer should be added to the mixture. Upon adding the 10% styrene for the second block ARGET ATRP polymerization, the appearance of a well-initiated polymer is observed. However, at greater conversions the results clearly demonstrate the production of a homopolymer/block copolymer mixture.leading to polymer contamination. [ 12 ] Activators regenerated by electron transfer (ARGET) ATRP was developed to offset the sensitivity of normal ATRP. ARGET ATRP uses a reducing agent, often ascorbic acid [ 13 , 14 ] or tin(II) 2-ethylhexanoate [Sn(EH) 2 ], [ 15 , 16 ] to consume the oxygen impurities that can inhibit the polymerization, thus reducing the sensitivity of this novel living system. The ease of polymerization creates low polydispersity homopolymers with many uses in future applications. [ 17 , 18 ] Block copolymer polymerization requires effi cient initiation of the fi rst and second block so that a lowpolydispersity block copolymer is formed. After the fi rst block has been polymerized, it is used as the macroinitiator for the subsequent polymerization of a different monomer. However, the macroinitaitor is chemically different from the initiator originally used to synthesize the fi rst block. [ 19 , 20 ] It has been found that for normal ATRP the initiation equilibrium constants are of the following order: acrylonitrile > methacrylates > styrene ≈ acrylates > acrylamides > > vinyl chloride > vinyl acetate. This order must be obeyed to produce a well-initiated polymerization and hence growth from the macroinitiator [i.e., the poly(methyl methacylate) (PMMA) must be extended by

Synthesis and applications of polystyrene-block-poly(N-vinyl-2-pyrrolidone) copolymers

“…Normally, very narrow Ɖ values (M w /M n ≤ 1.2) are obtained at low monomer conversion rates and/or by using solvent in the polymerization [25,37,38] . In the present work, we conducted the PS polymerization in bulk resulting Ɖ values slightly above very narrow Ɖ values (M w /M n ≤ 1.2) but still in the range of CRP Ɖ values (M w /M n ≤ 1.5).Thus, this work is in agreement with literature reported Ɖ values [4,6,[20][21][22]25,35] . DSC heating curves of the PS-b-PVP copolymers is shown in Figure 3.…”

“…These macromolecules are made up of two chemically different homopolymer blocks (A and B) combined as AB or ABA: one being hydrophilic and the other being hydrophobic. Polystyrene is a classic example of a hydrophobic glassy polymer frequently synthesized via CRP techniques [4][5][6][7] . On the other hand, an example of hydrophilic polymer is poly(N-vinyl-2-pyrrolidone) (PVP) which has been synthesized via CRP in the last few years [8][9][10] .…”

Catalytic Halogen Exchange in Miniemulsion ARGET ATRP: A Pathway to Well‐Controlled Block Copolymers

“…[ 9b,15 ] In ARGET ATRP catalytic amount of CuCl 2 did not improve chain extension as compared to CuBr 2 . [ 16 ] However, if sufficient amount of Cl − is available, even with a catalytic amount of Cu catalyst, C−Br chain ends can be successfully converted to C−Cl chain ends under catalytic halogen exchange ( c HE) conditions. [ 17 ]…”

Dual electrochemical and chemical control in atom transfer radical polymerization with copper electrodes

“…For example, controlled polymerizations were obtained with weak ligands such as bpy or PMDETA. [39][40][41][42][43] MMA also requires very active initiators such as ethyl 2-bromophenylacetate or 2-bromopropionitrile (BPN) to balance the propagating radical reactivity and avoid the penultimate effect. 39,44,45 We attempted SARA ATRP of MMA in ethanol initiated by BPN at 50 C and catalyzed by [Cu II TPMA] 2+ (TPMA ¼ tris(2-pyridilmethyl)amine), utilizing catalytic halogen exchange (cHE, with 0.05 M Bu 4 NCl) to suppress the mismatch of reactivity.…”