Group Transfer Polymerization of n-Butyl Acrylate with Lewis Acid Catalysts. 1. Kinetic Investigation Using HgI2 as a Catalyst in Toluene

Abstract

The group transfer polymerization (GTP) of n-butyl acrylate using l-methoxy-l-(trimethylsiloxy)-2-methyl-l-propene as an initiator and HgL as a catalyst in toluene is much slower compared to nucleophilic-catalyzed GTP; half-lives are in the range of minutes to hours. Induction periods are observed which are attributed to the formation of trimethylsilyl iodide (TMSI). The polymerization follows first-order kinetics with respect to the concentrations of initiator and catalyst. With respect to concentration of monomer the reaction is of first-order internally but follows an external reaction order of 1.52 due to the higher polarity of the reaction medium at higher monomer concentrations. The degree of polymerization is controlled by the ratio [M]o/[I]o, and the molecular weight distribution is narrow and can be described by a modified Poisson distribution. Generally, MJMn < 1.2. It is proposed that the active species are formed from initiator, catalyst, and TMSI.

Stereospecific Group Transfer Polymerization of Methyl Methacrylate with Lewis-Acid Catalysis—Formation of Highly Syndiotactic Poly(methyl methacrylate)

“…On the other hand, the silyl iodide co-catalyst has been supposed to activate both initiator and growing chain-ends in the GTP. 17,18 With our proceeding finding of stereospecific GTP of crotonates, 10,11 the present GTP of MMA extends the possibility of stereocontrol in GTP through the use of appropriate Lewis-acid catalysts, though the highly syndiotactic PMMA is formed as a part of the whole product and, as a consequence, the fractionation process is inevitable as in the case of the early stage of isotactic-specific polymerization of propylene invented by Natta. 19 However, distinctively different properties that the PMMA exhibits, such as high solvent-resistance, should be attractive both industrial and scientific viewpoints.…”

Preparation of Disyndiotactic Poly(methyl crotonate) by Stereospecific Group Transfer Polymerization

“…It should be noted that the disyndiotactic structure of this hexamer contains a configurational disorder at the chain-end; the structure is not (Et) 5 but (Et) 4 Ee. In a similar manner as described above, single crystals suitable for X-ray analysis were obtained from the predominant stereoisomer of tetramer ( diastereomeric purity 69% ).…”

“…The main chain of this hexamer adopts an extended all trans conformation, and the stereoregularity can easily be identified as a disyndiotactic structure. configuration of II asymmetric carbon atoms in this hexamer is expressed by (Et) 4 Ee according to the notations defined in our previous paper. 15 The capital letters E and T denote the erythro and threo diads, respectively, in a monomer unit.…”

“…4 • 5 Before this finding, direct preparation of poly( methyl crotonate) from its monomer had been considered to be difficult. As a commonly observed feature of crotonates, methyl crotonate gives no polymer by a free radical mechanism.…”

Enhanced Stereocontrol in Disyndiotactic-specific Group Transfer Polymerization of Methyl Crotonate—Stereochemical Evidence of Group Transfer

“…12 The combined catalyts HgI 2 /R 3 SiI has been known effective for the GTP of acrylates. 13 The predominant stereochemical structure of poly-(methyl crotonate) (PMC) thus formed was found disyndiotactic (Scheme 2) by X-ray analysis of the oligomers and NMR spectroscopy of the polymers and oligomers. 14 1 H NMR spectra indidated that the polymer obtained with 1-methoxy-1-(triethylsiloxy)-2-methyl-1-propene (2) has higher stereoregularity than that with 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene (1).…”