# 2-Methoxy-4-Vinylphenol as a Biobased Monomer Precursor for Thermoplastics and Thermoset Polymers
## 3 Results
### Thermosetting Applications  
Taking advantage of the styrene-like functionality of MVP, biobased difunctional monomers were prepared by reacting the phenol with brominated alkanes, resulting in divinylbenzene (DVB)-like monomers (Scheme 1). In detail, two MVP units were linked with an aliphatic chain consisting of three, six, or 10 carbons, referred to as 1,3-MVP, 1,6-MVP, or 1,10-MVP, respectively. The increase in aliphatic chain length was hypothesized to reduce the \(T_{\text{g}}\) values of the networks when crosslinked with thiol-bearing reagents and, by extension, to modulate the mechanical properties [44; 47]. The protocol used in this study resulted in relatively high yields with satisfactory biobased characteristics, as described through AE, E, and BBCC (Table S11). AE reached high values, i.e., on average 70%, for all DVB-like monomers synthesized. E ranged between 60 and 73, which is higher than the monomers synthesized for the thermoplastic applications. This is because the synthetic approach used to prepare the DVB-like monomers required additional purification steps including additional solvents [42]. The BBCC was found to decrease from 85% to 65% upon increasing the aliphatic chain length connecting the MVP units, which resulted in similar BBCC values to other functional biobased monomers in the literature (Table S12) [41]. Two thiol-bearing crosslinkers were used, containing three or four thiols on average, referred to as 3T and 4T, respectively, to investigate the effect of both the aliphatic chain length and the number of crosslinks on the thermosetting films. The protocol to prepare the thermosets was based on the melting temperature of the DVB-like monomers (around 100 \({}^{\circ}\)C, Table S4). An initial investigation of the crosslinking reaction was carried out in DSC by mixing the thiol-bearing reagents with the DVB-like monomers and monitoring the curing procedure (Figure S37). According to the curing peaks listed in Table S8, the  
Figure 2: DMA thermograms of MVP-based thermosets: (**a**) storage modulus (E’) and (**b**) tan\(\delta\) as a function of temperature. lowest curing temperature was \(\sim\)110 \({}^{\circ}\)C. However, the DSC experiments were performed under nitrogen atmosphere, which was hypothesized to reduce the curing temperature. Therefore, higher temperature was used for the preparation of thermosets. In particular, the thermosets were prepared in an oven by initially melting the DVB-like monomers at 125 \({}^{\circ}\)C, mixing them with the thiol crosslinkers, and then leaving them for 24 h at 125 \({}^{\circ}\)C (Figure S34). The extent of curing was assessed by the almost complete disappearance of C=C (\(\sim\)1650 cm\({}^{-1}\)) and -SH (\(\sim\)2600 cm\({}^{-1}\)) peaks in FT-IR spectra (Figure S33), indicating a high curing degree [48]. This protocol was chosen for two reasons: (i) the reduction in undesired chemicals such as solvents and initiators; (ii) the relatively low melting point of the DVB-like monomers, which acted as solvents for the thiol-bearing crosslinkers. The thermal properties of the thermosets were primarily affected by two parameters: (i) the aliphatic chain length between the DVB-like monomers; (ii) the number of crosslinks. As seen in Table 2 and Table S9, by increasing the aliphatic chain length, the \(T_{g}\) and \(T_{m}\) values decreased as shown before for the MVP-derived homopolymers, due to the increase in chain mobility [44]. Moreover, \(T_{g}\) was increased by increasing the number of crosslinks between the DVB-like monomers and the thiol crosslinkers, since the mobility was decreased [47]. Furthermore, according to the TGA results (Table S7), \(T_{\text{deg}}\) was seemingly unaffected by the aliphatic length between the MVP units when the standard deviation was accounted for. However, \(T_{\text{deg}}\) seemingly increased upon increasing the number of crosslinks when comparing the thermosets that were cured with 3T or 4T. This is to be expected, as increasing the number of crosslinks should improve the thermal properties [49].