Oxetane monomers

The molecular weight values of poly(TMC) obtained from oxetane and C02 in the presence of a (salen)CrCl/n-Bu4NN3 catalyst system were generally lower than the theoretical values (Mn = 11050 Mn (theoretical) = 85 000). This situation was most likely due to a chain transfer mechanism arising from the presence of trace amounts of water in the system. However, when the catalytic runs were carried out under rigorously anhydrous conditions, the molecular weights more closely tracked the predicted values. 

Finally, another method commonly used to characterize these copolymeric materials is that of matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. When using this technique, it is possible to investigate the molecular weight distributions, end groups, and polymer constitution of low-molecular-weight samples [63], MALDI-TOF may also provide vital 

---

The equilibrium position and subsequent rate of ring-opening differed significantly with the nature of the cyclic ether monomer. For example, the monomers, PO and oxetane, which have similar steric requirements and significantly different pKb values (6.94 and 3.13, respectively) [63], would be expected to bind to the metal center quite differently. As shown in Scheme 8.8, solution IR spectroscopy revealed that, in the presence of a large excess of oxetane monomer, the (salen)Cr(N3)2 species existed as an equilibrium mixture, greatly favoring the neutral oxetane-bound species [39]. 

The field of metal-catalyzed copolymerization of oxetanes and C02 will continue to flourish, due not only to the versatility of the reaction but also to the aliphatic polycarbonate products being important components of thermoplastic elastomers that, in turn, have huge potential in medical applications such as sutures, drug-delivery systems, body, and dental implants, and tissue engineering. The exploration of other oxetane monomers (Figure 8.17) such as 3,3-dimethyloxetane and 3-methoxymethyl-3-methyloxetane, will surely provide a multitude of applications... 

CHEC(1984) and CHEC-II(1996) discuss the acid-catalyzed transformations of oxetanes including ring expansion to THFs and formation of cyclic orthoesters <1984CHEC(7)363, 1996CHEC-II(1)721>. They also include many examples of the use of oxetane monomers in cationic polymerization reactions, giving ready access to polyethers. 

Reports of anionic polymerization reactions of oxetane monomers are less common in the literature, than the generally applied cationic method. While unsubstituted oxetanes have been successfully converted to their corresponding... 

A series of water-dispersible, surface-active poly(fluorinated oxetane)s was prept sd by ring-opening polymerization of fluorinated oxetane monomers using Lewis acid catalysis <02L5993>. 

Mono- and di-substituted oxetane monomers containing 2,2,2-trifluoroethoxy methyl substituents have been prepared. These agents were then used to prepare elastomers, thermoset plastics, and related articles where a very low surface energy was required. 

Ring-opening cationic polymerization of a perfluoroalkyl-substituted oxetane monomer using a Lewis acid catalyst and a diol initiator leads to an amphiphilic a, co-diol. Sulfation of the terminal hydroxyl groups leads to an anionic bola-amphiphile. 

By the addition of the oxetane monomer (Figure 19.4) to the hydroxyl groups a much more symmetrical structure is obtained [15] as compared to glycidol, because two primary hydroxyl groups, of equal reactivity are formed (reaction 19.11). 

The activation energy of polymerizations of oxetane monomers is higher that that of tetrahy-drofuran (see next section). This indicates that the orientation of the cyclic oxonium ion and the monomer is looser in the Siv2 transition state" ... 

Preparation of silicon-containing oxetane monomers and their polymerization was also investigated by Sangermano et al. Following monomers were reported ... 

Scheme 11 Preparations of a difluoramino-substituted oxetane monomer and polymer...

Oxetane monomers and telechelics. 3-Bromomethyl-3-methyloxetane, BrOx, served as the starting material for the fluorous and other oxetane monomers described in sections 10.2-10.5 (Figure 10.1). The synthesis of BrOx is conveniently carried out on a large scale from l,l,l-tris(hydroxymethyl) ethane as shown in Equations 10.1 and 10.2 [23-25]. Fluorous and other oxetane monomers were prepared from BrOx by variations of the Williamson synthesis (Equation 10.3) in a manner similar to that described by Malik [26,27]. 

N2 is also present. No doubt, the decomposition process begins in the methylazide group [10]. Fast thermolysis of the azidomethyl oxetane monomers that polymerize to form AMMO and BAMO yields products that are... 

Chlorinated Polyether [poly-3,3-bis-(chloromethyl) oxacyclobutane, Penton ] A corrosion-resistant thermoplastic obtained by polymerization of chlorinated oxetane monomer, the oxetane being derived from Pentaerythritol, to a high molecular weight... 

Toagosei in Japan have developed oxetane monomers. These four-membered cyclic ether monomers are claimed to give superior properties to cycloaliphatic epoxies. 

Oxetanes are slightly more basic than epoxides and have similar ring-strain energies. For this reason, oxetane monomers are also excellent candidates for use in UV curing applications. However, only monofunctional oxetane monomers were known and these were available only in small quantities from chemical supply houses. Crivello and Sasaki and Sasaki et used novel synthetic methods to prepare a series of mono- and diftmctional 3,3-disubstituted oxetane monomers that are now available on a commercial scale. In many cases, the oxetane monomers are used in combination with epoxide monomers in UV curing applications. ... 

Fluroinated oxetane monomer (FOX) was added to DOX in the range between 5 to 15 wt%. In this range of composition homogeneous and transparent formulations were obtained. The highest concentration of the fluorinated monomer in the reference resin, DOX, as assessed by visual inspection, corresponds to the solubility limit. 

MiWA Y, TSUTSUMI H and OISHI T (2002), Novel polymer electrolytes based on mono-and bis-oxetane monomers with oligo (ethylene oxide) units . Electrochemistry, 70(4) 264-269... 

---