Degradable Poly(alkyl acrylates) with Uniform Insertion of Ester Bonds, Comparing Batch and Semibatch Copolymerizations

Abstract

Poly(alkyl)acrylates are a major class of nonbiodegradable polymers which are difficult to recycle due to an all-carbon backbone. Introducing a certain number of ester bonds in the backbone via radical ring opening copolymerization of acrylates with 2-methylene-1,3 dioxepane (MDO) improves its degradability and may be promising for chemical recycling. The current work examines the influence of monomer addition profiles on the copolymerization of acrylates with MDO. We improved the homogeneity of the MDO insertion through a semibatch approach, which was demonstrated by the molecular weight distribution of fragments after alkali degradation. By detailed NMR analysis, we identified the incorporation of MDO ring retained units, formation of branches on acrylate units, and formation of branches on MDO ring open units as the key side reactions. Theoretical calculations showed that mainly kinetic factors influence the outcome of the polymerization.

Connecting polymer synthesis and chemical recycling on a chain-by-chain basis: a unified matrix-based kinetic Monte Carlo strategy

“…35% out of MDO units. It further follows that in each of the 3 situations one observes so-called composition drifting [114][115][116][117] with the monomer mixture being depleted in MMA so that chains formed later on are more rich in MDO units. For example, for fMMA,0=fMDO,0=0.5, the chains contain as much as 80% MMA units at low overall monomer conversions, while polymer chains formed at high overall monomer conversion (> 0.80) contain no MMA units at all.…”

“…To obtain a PMMA-like product with an even beter degradability one should consider (i) either increasing the feed fraction of MDO, (ii) choose a comonomer combination with more suitable monomer reactivity ratios, preferably close to 1, or (iii) synthesize the copolymer according to a semi-batch procedure. 117 However, for the current purpose of highlighting the proof-of-concept of connecting synthesis and recycling of FRP-made copolymers a suboptimal set of reaction conditions featuring severe drifting is better suited to illustrate the general capability of the kMC tool. It should be further stressed that Figure 11 is also characterized by an excellent mathematical description of the tail of the distribution, as witnessed by the limited noise at the higher molar masses, highlighting the relevance of the compression-based matrix modeling framework in case high average chan length polymers are targeted.…”

Prediction of the Oligomer Distribution after Degradation of (Co)Polymers with Inserted Break Points

“…[ 2 ] Most MDO copolymerizations (see Figure ) are characterized by unfavorable reactivity ratios; in batch reactions this leads to strong composition drift, [ 9 ] sometimes resulting in homopolymer formation of MDO and/or incomplete conversion of the CKA's. [ 10,11 ] We recently have shown experimentally that through application of semi‐batch monomer addition profiles (MAP), the incorporation of MDO in acrylate copolymers can be improved. [ 11 ] Besides ring‐opening, ring retain reactions can also occur; however, the majority of insertions follows ring‐opening mechanism [ 11 ] and in our calculations we neglect the ring retain possibility.…”

“…[ 10,11 ] We recently have shown experimentally that through application of semi‐batch monomer addition profiles (MAP), the incorporation of MDO in acrylate copolymers can be improved. [ 11 ] Besides ring‐opening, ring retain reactions can also occur; however, the majority of insertions follows ring‐opening mechanism [ 11 ] and in our calculations we neglect the ring retain possibility. Although the unfavorable reactivity ratios need to be overcome with respect to the incorporation and full utilization of the MDO monomers, at the same time the low reactivity ratio for MDO results in single MDO units in the chain (see Figure 1), which is actually beneficial for the effectiveness of later degradation in oligomers, as each MDO unit is used efficiently.…”

Synthesis of degradable and chemically recyclable polymers using 4,4-disubstituted five-membered cyclic ketene hemiacetal ester (CKHE) monomers

“…[1][2][3][4][5][6][7][8][9] In the eld of radical polymerization, degradable polymers are prepared via radical ring-opening polymerization of cyclic ketene acetals (CKAs), [10][11][12][13][14] for example, gaining signicant attention. Examples of CKA are 2-methylene-1,3-dioxepane (MDO), [15][16][17][18][19][20][21][22][23] 5,6-benzo-2methylene-1,3-dioxepane (BMDO), [24][25][26] and 2-methylene-4phenyl-1,3-dioxolane (MPDL) [27][28][29][30] (Scheme 1). CKAs are homopolymerized and co-polymerized with other vinyl monomers, affording degradable ester linkages in the polymer backbones.…”