Reverse atom transfer radical polymerisation (RATRP) of methacrylates using copper(I)/pyridinimine catalysts in conjunction with AIBN
2005; Elsevier BV; Volume: 42; Issue: 1 Linguagem: Inglês
10.1016/j.eurpolymj.2005.08.011
ISSN1873-1945
AutoresAdam Limer, David M. Haddleton,
Tópico(s)Synthetic Organic Chemistry Methods
ResumoN-n-Propyl-2-pyridylmethanimine, 1, N-n-octyl-2-pyridylmethanimine, 2, N-n-lauryl-2-pyridylmethanimine, 3, and N-n-octadecyl-2-pyridylmethanimine, 4 have been used in conjunction with copper(II) bromide and azo initiators for the reverse atom transfer radical polymerisation of a range of methacrylates. AIBN to CuIIBr2 ratios of 0.5:1, 0.75:1 and 1:1 give PMMA with Mn 11 500 g mol−1 (PDi = 1.24) (at 22% conversion), 12 500 g mol−1 (PDi = 1.06) (at 83% conversion) and 10 900 g mol−1 (PDi = 1.11) (at 84% conversion), respectively. A CuIIBr2 complex is demonstrated to be needed at the start of the reaction for good control over molecular weight and polydispersity as reactions using Cu(I)Br as catalyst yielded PMMA of Mn 31 000 g mol−1 (PDi = 2.90), reactions with no copper yield PMMA of Mn 33 000 g mol−1 (PDi = 2.95). The RATRP of styrene was carried out using CuIIBr2 as catalyst. AIBN to CuIIBr2 ratio of 0.5:1, 0.75:1 and 1:1 gave PS with Mn = 12 400 g mol−1 (PDi = 1.27) at low conversion, Mn = 15 500 g mol−1 (PDi = 1.11) and 12 400 g mol−1 (PDi = 1.38), respectively at ∼85% conversion. A series of block copolymers of MMA with BMA, BzMA and DMEAMA (15 600 g mol−1 (PDi = 1.18), 13 300 g mol−1 (PDi = 1.14) 15 300 g mol−1 (PDi) = 1.16), using a PMMA macroinitiator were prepared. Emulsion polymerisation of MMA using [initiator]:[Cu(II)Br2] ratio = 0.5:1 with Brij surfactant gave a linear increase of Mn with respect to conversion, final Mn = 112 800 g mol−1 (PDi = 1.42). Further reactions were carried out with [initiator]:[Cu(II)Br2] ratio = 0.75:1 and 1:1. Both giving PMMA with Mn ∼ 32 000 g mol−1 (PDi ∼ 2.4). These reactions exhibit no control, this is because the azo initiator is present in excess and all of the monomer is consumed by a free radical polymerisation as opposed to a controlled reaction. Particle size analysis (DLS) showed the particle size between 160 and170 nm in all cases.
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