Methyl tosylate Initiated polymerization

Scheme 8.25 Schematic representation of the methyl-tosylate-initiated CROP of cyclic irnino ethers indicating the isomerization from an imino ether to an amide moiety during polymerization as well as the R functionality of the monomer that determines the polymer side-chain functionality.

In addition, the propagating species of MeOZO polymerization with the methyl tosylate initiator is reacted with a higher alkyl primary amine to produce another type of non-ionic surfactant [9]. ... 

The living cationic ring opening polymerization (CROP) of 2-oxazolines was first reported in the 1960s [61, 62]. The polymerization can be initiated by an electrophile such as benzyl halides, acetyl halides, and tosylate or triflate derivatives. The typical polymerization mechanism for 2-alkyl-2-oxazoline initiated by methyl tosylate is shown in Scheme 6. 

A library of 4 chain extended homopolymers and 12 diblock copoly(2-oxazoline)s was prepared from 2-methyl, 2-ethyl, 2-nonyl, PheOx in a very short period of time [90]. The CROP was initiated by methyl tosylate and performed in acetonitrile at 140 °C in a single-mode microwave synthesizer. A total number of 100(50 + 50) repeating units was incorporated into the respective polymer chains. The concentration of the solutions and predefined polymerization times for each monomer and comonomer are summarized in Table 11. 

A theoretical model was developed to correlate molecular weight distribution of this system. This was compared to the experimental gel permeation chromatography trace with the theoretical model modified to Include the effect of the PEG central block, the spreading of the trace as it went through the columns and the slope of the log MW versus retention volume line. A good fit was found with kl/kp = 0.0070. When methyl tosylate was used to polymerize 2-lsobutyl oxazollne, a similar treatment of the data showed kl/kp = 0.22. The effect of the PEG Is explained as due to solvation of the Initial adduct by the neighboring ether group. 

Methyltosylate initiated polymerization In order to determine if the PEG part plays any significant role in initiation, a polymerization was carried out with methyl tosylate as initiator using M/I of 5.92. At complete consumption of monomer, unreacted methyl tosylate was still present (see Figure 4). The polymer produced had a broad molecular weight distribution, 1.39. kp/kl was estimated by... 

The polymer produced with methyl tosylate as initiator has one N-CHg group per chain and this methyl group could be observed in the NMR spectrum. By comparing the Integrals of N-CHj (a) and CH, (b) of the isobutyl side chains, the degree of polymerization was calculated. 

Litt claimed formation of block copolymers of 2-lauroyl-2-oxazoline and 2-methyl-2-oxazine by sequential polymerization 122). Methyl tosylate was the initiator and the polymerization was terminated by water. The proposed structure of the copolymer is ... 

Ring-opening polymerization reactions of several 2-substituted-2-oxazolines (i.e. 2-methyl, 2-ethyl, 2-nonyl, and 2-phenyl) in the presence of methyl tosylate as catalyst have been described by Schubert et al. (Scheme 14.14) [33-35]. The reactions were performed in the temperature range 80 to 200 °C inside a single-mode micro-wave reactor. In a typical run, 25 mL stock solutions of monomer-initiator-solvent were prepared before the polymerization. These stock solutions were divided among different reaction vials so each experiment was performed on a 1-mL scale. 

The same technique of the ring-opening polymerization under microwave irradiation conditions was subsequently applied to the synthesis of a library of diblock copoly(2-oxazoline)s in which a total number of 100 (50 + 50) monomer units were incorporated into the polymer chains [36]. As a result, 16 polymers were obtained with narrow polydispersity indexes (PDI < 1.30). The reactions were initiated by methyl tosylate and conducted in acetonitrile solution at 140 °C. After polymerization of the first monomer the reaction vessels were re-transferred to an inert atmosphere of argon, the second monomer was added, and the reaction mixture was again irradiated in a microwave reactor. 

Poly(2-oxazoline)s can be prepared by living cationic ring-opening polymerization of the 2-oxazoline monomers utilizing an electrophilic initiator, such as methyl tosylate or methyl triflate. Attack of the monomer onto this initiator leads to the formation of a cationic oxazohnium species and subsequent monomer attack leads to ring-opening while the newly added monomer ends up as a cationic oxazolinium chain end. As such, well-defined polymers can be obtained and the chain-end functionalities can be controlled during initiation and termination (Aoi and Okada, 1996). 

The synthesis of AMO involves treatment of 3,3-bis(chloromethyl) oxetane (BCMO) with sodium azide in the DMF medium at 85 °C for 24 h. Similarly, AMMO which is a monofunctional analog of AMO is synthesized by the azidation of chloro/tosylate product of 3-hydroxymethyl-3-methyl oxetane (HyMMO) with sodium azide in DMF medium at elevated temperatures. These energetic monomers are readily polymerized to liquid curable prepolymers with the help of boron trifluoride etherate/l,4-butanediol initiator system and the outlines of synthesis [147-150] of poly(BAMO) [Structure... 

Oxonium salts have been used as initiators in the polymerization of sulfides and amines as low-molecular-weight compounds (e.g. Et3OeBFJp)15,16) and as dicatio-nically living polyTHF 17,18) in the synthesis of diblock and triblock copolymers. Among alkyl esters and halides, tosylates, iodides, bromides, fluorosulfonates, and triflates were used in the polymerization of azetidines4,9,10 and aziridines 19,20). Methyl triflate forms the first alkylation product in the polymerization of 1-t-butyl-aziridine, which precipitates out of solution 19) ... 

The cationic polymerization of 2-(l-pyrrolidinyl)-2-oxazo-line (PyOZO) gave two different polymers by the selection of initiator. With methyl trifluoromethanesulfonate (triflate) (MeOTf) or methyl p-toluenesulfonate (tosylate) (MeOTs), the polymerization of PyOZO yielded poly(N-(l-pyrrolidinecarbo-nylimino)ethylene) according to the usual CROP (SIP). On the other hand, the polymerization of PyOZO with RX gave poly ((l,3-diazolidin-2-one-l,3-diyl)tetramethylene) via DIP (Scheme 11). In the latter polymerization, the OZO ring was opened and rearranged to a five-membered cyclic urea unit. 

A comparison of the rate of conversion of a-tosylamino- 3-thiolactone and a-(A -methyl-A -tosyl-amino)-j3-thiolactone calculated from the change of specific rotation with time is shown in Figure 8. Both monomers were polymerized under the same conditions in bulk at 110 °C with 3.2% of benzyl mercaptan as initiator. It is evident that the A -tosylamino derivative polymerizes much faster than A -methyl-A/ -tosylamino- 3-thiolactone. 

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