Poly(1,4‐cyclohexylenedimethylene‐1, 4‐cyclohexanedicarboxylate): analysis of parameters affecting polymerization and cis–trans isomerization

Abstract

Weatherable semicrystalline polyesters based on 1,4-cyclohexanedimethanol, 1,4-cyclohexanedicarboxylic acid (CHDA) or dimethyl 1,4-cyclohexane dicarboxylate (DMCD) can be prepared under normal melt-phase conditions, using titanium tetrabutoxide as catalyst. The effect of monomer ratio, reaction temperature and catalyst loading on the final polymer properties was studied. Under the proper polymerization conditions, poly(1,4-cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate) polymers with high molecular weight can be obtained. During polymerization, isomerization can occur towards the thermodynamically stable cis-trans ratio of 34-66 mol%. Carboxylic acid end groups can catalyze the isomerization and therefore the polymerization is more critical starting from CHDA rather than DMCD. Moreover, temperature control becomes a key factor to avoid or to limit isomerization. The study of the isomerization of the different monomers permitted a better understanding of the isomerization and therefore of the polymerization process

Ageing of PCCD aliphatic polyesters: Effect of stereochemistry and ionic chain terminals

“…They are named as PCCD-94, -90, -81, -52, according to the molar percentage of the trans isomer in the cyclohexylene units derived from DMCD, measured by 1 H NMR consistent with the procedure described in Ref. [4] (see Table 1). The aliphatic rings derived from CHDM have a trans percentage equals to 66 mol%.…”

“…The synthesis procedure is reported in Refs. [4,18]. After synthesis, samples were purified by dissolution in dichloromethane and precipitation in methanol.…”

“…Indeed, 1,4-cyclohexanedicarbonyl units could isomerize towards the cis/trans ratio that is thermodynamically stable (34/66 mol%) [4]. It comes out that after photoageing some samples do not maintain a full solubility in chloroform, as typical of non aged PCCDs, due to some modifications of the chemical structure described below.…”

“…Hence, PCCD has a high potential for a wide range of applications, especially after the recent improvements in synthesis procedures [1][2][3][4].…”

Resorcinol: A potentially bio-based building block for the preparation of sustainable polyesters

“…Dimethyl terephthalate and dimethyl isophthalate have been chosen in order to avoid very long reaction times and high temperatures due to the high T m of the corresponding diacids (above 300 °C). DMCD (100% trans isomer) was used instead of the corresponding diacid since carboxylic acids are well known to catalyse the isomerization from trans to cis isomer towards the thermodynamically stable cis/trans ratio (34/66 mol%), whereas the isomerization is less probable in the presence of diesters 30. The CHDA 66% trans, instead, can be used because isomerization does not occur: the thermodynamically stable cis/trans ratio is already present.…”