Iodine‐Transfer Polymerization (ITP) of Ethylene and Copolymerization with Vinyl Acetate

Abstract

Controlled radical polymerization of ethylene using different commercially available,c heap,a nd non-toxici odo alkyls is performed by iodine transfer polymerization (ITP) under mild conditions (100 8 8Ca nd 200 bar). The formed well-defined iodo end-capped polyethylene (PEÀI) species is very stable upon storage.N arrow molar-mass distributions (dispersities around 1.6) were obtained up to number average molar masses of 7300 gmol À1 .T he ethylene copolymerization by ITP (ITcoP) with vinyl acetate allowed to form ab road range of poly(ethylene-co-vinyl acetate) (EVA) containing from 0to85mol %ofV Ac unit. In addition, EVA-b-PE block copolymers or EVA-b-EVAg radient blockc opolymers with different content of VA cinthe blocks were obtained for the first time using ITP.F inally,r eactivity trends were explored by at heoretical mechanistic study.T his highly versatile synthetic platform provides astraightforwardaccess to adiverse range of well-defined PE based polymer materials. À1 represent reaction rate coefficients for iodine transfer.

Block Copolymers Based on Ethylene and Methacrylates Using a Combination of Catalytic Chain Transfer Polymerisation (CCTP) and Radical Polymerisation

“…Thee xpected hydrogen signals characteristic for PE are observed:( i) initiation by isobutyronitrile primary radicals, from AIBN,(1.09 ppm);(ii)initiation by the radicals formed after chain transfer to solvent, DMC,( 3.53 and 3.98 ppm); (iii)intramolecular and intermolecular chain transfer inherent in ethylene radical polymerisation leading to long and short-chain branching (0.61-0.90 ppm);(iv) trace presence of vinyl end groups (4.93 and 5.76 ppm) as already observed. [11,12,15,58] Signals of low intensity,i nt he 5.5 to 6.5 ppm region, corresponding to the vinylic hydrogens of the unreacted MMA 2 ,a re observed, as expected (77 % conversion after 3has shown by GC,T able 2). Together with the signals at 3.5 ppm corresponding to the methoxy hydrogens in both MMA 2 and the polymer,t hese assignments confirm ar eaction between propagating PE macroradicals and MMA 2 .C ontrary to what might have been expected the absence of vinyl protons other than those of residual MMA 2 indicates that the fragmentation path of Scheme 1i ss low relative to these other processes.However, it does not permit us to discriminate between block and graft architectures in the Scheme 1.…”

“…[9] Radical polymerisation of ethylene under mild conditions can be challenging, [10] and only recently,t he controlled (co)polymerisation of ethylene with more polar monomers has been reported. [11][12][13][14][15][16][17] These discoveries have allowed for the design of more complex macromolecular architectures based on PE segments such as gradient and block copolymers. [15,[18][19][20][21] Although there is asignificant academic interest in the use of RDRP techniques,s uch as atom transfer radical polymerisation (ATRP), nitroxide mediated polymerisation (NMP), organometallic mediated radical polymerisation (OMRP) or reversible addition-fragmentationc hain transfer (RAFT), their use for industrial applications has been somewhat limited.…”

“…[11][12][13][14][15][16][17] These discoveries have allowed for the design of more complex macromolecular architectures based on PE segments such as gradient and block copolymers. [15,[18][19][20][21] Although there is asignificant academic interest in the use of RDRP techniques,s uch as atom transfer radical polymerisation (ATRP), nitroxide mediated polymerisation (NMP), organometallic mediated radical polymerisation (OMRP) or reversible addition-fragmentationc hain transfer (RAFT), their use for industrial applications has been somewhat limited. [22,23] Improvements in this area are continually being made,h owever,t he monomer compatibility,o ften the presence of unwanted end-groups in the polymeric chains,w hich are difficult to remove and/or change the colour of the material, the difficulty to scale up and the cost/performance ratio are some of the still existing limitations.…”

Statistical and Block Copolymers of Ethylene and Vinyl Acetate via Reversible Addition‐Fragmentation Chain Transfer Polymerization

“…This distortion of the type of signal with the VAc content in EVA was already observed when synthesizing EVA using ITP. [ 28 ] This is indeed a very useful tool to quickly identify if chain extension takes place when block copolymers containing different contents of VAc in the two blocks are targeted (see below). The different VAc contents were obtained by varying the E pressure and/or the VAc volume, and a detailed list of the polymerization conditions and results is included in Table S3, Supporting Information.…”

“…[ 26,27 ] This growing understanding of the underpinning mechanisms that governs the control led us to successfully consider and apply ITP to E as this polymerization technique does not involve CTAs with stabilizing groups. [ 28 ] Copolymerizations of E and VAc using ITP were also thoroughly investigated and as expected allowed not only to produce well‐defined EVA and VAE but also block copolymers based on EVA or VAE segments.…”