¹³C NMR Study of the Grafting of Maleic Anhydride onto Polyethene, Polypropene, and Ethene−Propene Copolymers

Abstract

The reaction products from the radically initiated grafting of specifically 13 C-enriched maleic anhydride ([2,3-13 C2]MA) onto polyethene, isotactic polypropene and ethene-propene copolymers in the melt and in solution are investigated using noise-decoupled and 1D inadequate 13 C NMR spectroscopy. The sites of attachment and the structures of the grafts depend on (co)polymer composition. In random EPM, MA attaches to methylene and methine carbons in the backbone. In alternating EPM, MA attaches solely to polymer methines, indicating that (CH2)m sequences with m > 3 are needed for MA attachment to backbone methylene carbons. In the copolymers and in IPP, grafts are single succinic anhydride rings; in HDPE and LDPE short MA oligomers are also present. In polyolefins containing polypropene sequences, chain scission can yield structures in which the anhydride ring is attached to the chain terminus via a fully substituted double bond.

Grafting of maleic anhydride on polypropylene by reactive extrusion: effect of maleic anhydride and peroxide concentrations on reaction yield and products characteristics

“…Then, they were characterized by infrared spectroscopy, by considering two specific peaks [31]: the first one at 1790 cm -1 concerns the carbonyl groups, and the second one at 1167 cm -1 concerns the CH 3 groups. The ratio of these peak areas is the carbonyl index (Index = A 1790 /A 1167 ), which can be related to the percentage of grafted MA using a calibration curve [26,32] …”

“…Despite the number of publications on the topic, there are still some discussions on particular reactional mechanisms [11,[24][25][26][27]. However, in a general way and according to Nachtigall et al [28], we can propose the following simplified mechanism: the free radicals generated by the peroxide decomposition lead by hydrogen abstraction to tertiary alkyl polymer radicals.…”

Synthesis of maleic anhydride grafted polyethylene and polypropylene, with controlled molecular structures

“…The formed macroradical 1,20 -22 in polyolefin subsequently reacts with maleic anhydride monomer. Many experimental results show that the incorporated MA unit is predominately a single succinic anhydride group, 22,23 due to poor homopolymerization capability of MA monomer. As expected, many side reactions also take place during this free radical grafting reaction.…”

Maleic anhydride‐grafted linear low‐density polyethylene with low gel content

“…Interestingly, T c values of LLDPE-g-MAH copolymers are varied a little, while T c of LLDPE-grafted acrylic acid is higher 3-48C than pristine LLDPE due to the nucleation of polyacrylic acid grafted onto LLDPE chains [24]. It is because MAH grafted onto LLDPE is in the form of single succinic anhydride ring as well as short oligomer [25], which has no obvious nucleation to the crystallization of LLDPE chains.…”