Organosilicon crown compounds in the anionic polymerization of ε‐caprolactam

Abstract

Many investigations have recently been published on the role of crown compounds and cryptates in polymerization processes, but only few of them concerned cyclic siloxanes'*'). Depending on the hole size of these compounds, several metals and metal ions can be complexed by them due to the high polarizability and coordination capability of the oxygen atoms in the ring. The effect of the counter-ion in the polymerization step can well be studied by means of these derivatives.The present paper aims at the investigations of the effect of crown compounds as well as t'lat of the counter-ion in the anionicpolymerization. As a model, activated anionic polymerization of E-caprolactam (CL) was studied.The counter ions of the chosen activator system were Li', Na', and K'; the applied promoter was hexamethylenediisocyanate (HMDI) and octamethylcyclotetrasiloxane (D4) was used as crown compound (bp 175°C at 760 Torr). Experimental PartCL containing 1,5. lo-' M of activator in lactamate form (L) was produced by refluxing the mixture of CL with the calculated amount of sodium or potassium hydroxide at 160°C for 30min under reduced pressure (5 Torr). The system including lithium lactamate was prepared by addition of the indicated amount of metallic lithium to the molten CL at 140°C. The used crown compound was added to the molten mixture of CL and alkali lactamate in concentrations such that the counter-ion content was complexed to 0, 12,5, 25, and 50 percent-supposing a complexing ratio of 1:l. These compositions are marked with a, b, c, and d, respectively, in the Table and in the Figure. Glass vials, fit into the differential scanning calorimetry (DSC) instrument (Unirelax, Tetrahedron Ass., Inc.), were filled with a known amount of HMDI+CL adduct having a mole ratio of activator to promoter of 2: 1 in the ready-to-polymerize system.The mixture of CL with the activator and the crown compound was added very quickly into the above vial in molten form followed by vigorous shaking until the promoter adduct was dissolved. Then the vial was sealed and quenched by liquid nitrogen. This procedure should not take more than 1 min. The sealed vials were stored at -15°C till the DSC recording.DSC curves were recorded at a heating rate of 1 or 1,5"C/min. Results and DiscussionFig . 1 shows the DSC curves of the system containing Li' counter-ion. The thermogram recorded in the absence of D4 (see curve a on Fig. 1) exhibits only a slight effect refemng to the polymerization process. The product is actually a low-molecular-

Optimizing conditions for anionic polymerization of caprolactam for inkjetting

“…According to different reports,7–14 three main parameters play the most significant role in APCL. These are catalyst (i.e., type and concentration), activator (i.e., type and concentration), and also initial polymerization temperature.…”

DSC investigations on the alkaline polymerization ofε-caprolactam

“…In the activated anionic polymerization initiated by LiL, the polymerization and crystallization processes could be separated merely from the heating curve, without a knowledge of the crystallization peak of the cooling curve [l]. For numerical evaluation of the thermal effects, the melting peak of CL monomer was used as internal standard [2]. For the polymerization heat of CL, -135 _ _+ 15 J/g was obtained by the curve-resolving of DSC curves recorded with samples of various compositions.…”

Polymers and Related Composites via Anionic Ring-Opening Polymerization of Lactams: Recent Developments and Future Trends

“…Attempts were also made to influence the progress of anionic lactam polymerization through additives which may cause complexation with the counter-ion or influence the anion formation and anion stabilization. For such purposes crown compounds [20] and ionic liquids [21] have been tried.…”