Preparation and properties of polymers of secondary alkyl crotonates and related monomers

Abstract

synopsisThe anionic p,olymerization of a variety of secondary alkyl crotonates and related monomers initiated by fluorenyllithium (complexed with tetrahydrofuran) in toluene a t -78°C. is reported. No crystallinity could be developed in any of the samples, and nuclear magnetic resonance was uninformative about possible tacticity. The polymerization techniques were ineffective when applied to n-alkyl esters. Polymer was obtained from isopropyl cinnamate and N,N-dimethyl crotonamide, but not from isopropyl thiocrotonate or isopropyl Zpentenoate. The physical properties of injectionmolded specimens of polymers of isopropyl, s-butyl and cyclohexyl crotonate were examined in some detail; the polymers exhibited a desirable combination of high service temperatures and good impact resistance for a vinyl homopolymer but were extremely difficult to mold. Poly(isopropy1 crotonate) had a heat distortion temperature of 125OC. at 85 psi, a notched h o d impact of 2.4 ft.-lb./in. of notch, and a flexural modulus of 274,000 psi.Intense interest in the stereoregular anionic polymerization of acrylic and methacrylic esters during the past ten years has led several investigators to examine the polymerization of related a,@-unsaturated esters with substituents other than hydrogen on the @ carbon atom of the double bond, the simplest of these systems being esters of crotonic acid. Miller and Skogman' have reported studies of the polymerization of t-butyl crotonate; they showed that there were limitations on the nature of the anionic initiator that could be employed, both in the ability to initiate polymerization and in the degree of crystallinity of the polymer formed. No physical properties of the polymer were reported other than a glass transition temperature of 86°C. Natta et a1.2 have disclosed the preparation of crystalline poly(t-butyl crotonate) and poly(isopropy1 crotonate), the latter softening at 27O-29O0C., by polymerization in toluene at -78°C. with ether-free phenylmagnesium bromide as initiator.Since the completion of our experimental program Makimoto, Tanabe, and Tsuruta have reported the polymerization of methyl crotonate with calcium zinctetraethyl complex in toluene and have stated that this

Unique acrylic resins with aromatic side chains by homopolymerization of cinnamic monomers

“…Using the reaction conditions of Entry 4 but extending the reaction time to 28 days increased the yield and M n of the obtained polymer from 43 to 81% and from 13,000 to 18,100 g mol −1 , respectively (Entry 10, Table 1). This result is a remarkable example of the convenient homopolymerization of cinnamates under mild conditions as compared to the literature data [10][11][12][13][14][15][16][17][18] . Furthermore, we investigated the effect of the catalyst in the GTP system.…”

“…Cinnamic monomers, which are known to be difficult to polymerize by classical polymerization methods, were successfully homopolymerized by the GTP technique through the general GTP mechanism. Compared with literature examples [10][11][12][13][14][15][16][17][18] , our approach realized convenient homopolymerization of cinnamates under relatively mild conditions. This behavior is likely due to the easy repetition of the Michael reaction in the GTP system.…”

“…However, convenient addition polymerization of cinnamic monomers has rarely been reported owing to steric hindrance of the aromatic substituent located at the β-position and delocalization of the electrons throughout the molecule via unsaturated π-bonding [10][11][12][13][14][15][16][17][18] . Sapiro et al reported the polymerization of ethyl cinnamate under harsh high-temperature and high-pressure conditions (125°C, 4,000 atm) 10 .…”

“…Alkyl crotonates are α,β-unsaturated carbonyl compounds with a methyl group at the β-position. Similar to cinnamic monomers, there are well-known difficulties in using alkyl crotonates (or crotonic acid) as a monomer to produce polymers with sufficient molecular weights by classical radical polymerization methods using AIBN or benzoyl peroxide and by typical anionic polymerization methods using an alkyl lithium or Grignard reagent [17][18][19][20][21][22] . Group-transfer polymerization (GTP) systems for various alkyl crotonates have been developed using a Lewis acid (HgI 2 or CdI 2 ) as a catalyst and iodotrialkylsilane as a cocatalyst [23][24][25][26][27] .…”

Kinetic modeling study of the group-transfer polymerization of alkyl crotonates using a silicon Lewis acid catalyst

“…1,2 Because of β-substituent steric hindrance and/or an electronic factor, there are well-known difficulties in using these compounds as monomers to produce homopolymers with high molecular weights via conventional radical polymerization methods based on 2,2′-azobisisobutyronitrile or benzoyl peroxide and via typical anionic polymerization methods based on alkyl lithium or Grignard reagents. [3][4][5][6][7] Recently, we reported the group-transfer polymerization (GTP) method for the homopolymerization of various alkyl crotonates using only an organic acid catalyst, such as N-(trimethylsilyl)bis(trifluoromethanesulfonyl)imide (Tf 2 NSiMe 3 ), which is a silicon Lewis acid (LA), and 1-trimethylsiloxyl-1-methoxy-2-methyl-1-propene (MTS) as the initiator. 8,9 In general, organocatalysis without metal compounds is beneficial for industrial applications because of the well-known advantages of metal-free polymeric products and processes.…”