Investigation of the factors causing chain structure change in ionic diene polymerization

Abstract

0 VA, N auchno-I ssledovalelski!£ I nstitut Sintelicheslcogo Kauchuka im S. V . Lebedeva, Leningrad, U.S.S.R . IFor solving the problem of cis-polyisoprene or cis-polybutadiene synthesis one must take into consideration not only the nature of the catalyst determining the character of the monomer addition during the polymerization but also secondary reactions proceeding in the polymer cha in under the influence of the eatalytic complex components. We have found that titanium halides and organoaluminum compounds cause isomerization of the cis uni ts of natmal rubber into the trans units. 1 The percentage of different configurations of the polymer chain uni ts has been determined by infrared spectmscopy from the absorption at 840 em. -l. In some cases it has been dete rmined qualitatively from t.he absorption bands at 1300 and 1100 em. -1 • The data on the relative proportion of cis and trans units are only qualitative sin ce, simultaneously with the polymerization proce s, a considerable TABLE I Tso mPriza tion of Na tura l Ruhlw r ( in a2 % Benzene Solution during 10 hr. ) % by % of units from total number of Hn Rat11ratNI " ·eigh t units o f T Ptnp. , Vnsatura t ion , Catalyst rubber oc. % Ct S tran s DO 99.2

The Reaction of Polyisoprene With Titanium Tetrachloride

“…Significantly, the calculated unsaturation values were less than the corresponding chemical values by approximately the same amounts for both cis-and trans-polyisoprenes. Nevertheless, the spectroscopic and chemical unsaturation values are in close enough agreement to show that isomerization cannot be an important part of the overall reaction of polyisoprene with TiC14 as claimed by Dolgoplosk and co-workers (17)(18)(19). Accordingly, we are justified in disregarding changes in D due to possible isomerization when calculating the residual -C(CH3)=CH-units in the manner shown in Table I.…”

“…Recently, Dolgoplosk and co-workers (17)(18)(19) reported that natural rubber in benzene undergoes such an isomerization when treated a t 80 to 90' C with titanium tetrachloride, anhydrous hydrogen chloride, or various organometallic compounds. Their results, however, are open t o question on the following grounds.…”

Oligomerization and Polymerization of Isoprene Catalyzed by Alkylaluminium with Different Structures

“…20 世纪 50 年代以来, 许多质子酸或路易斯酸(如 TiCl 4 、 AlCl 3 和 AlEtCl 2 等)作为阳离子引发剂, 催化异戊 二烯、丁二烯聚合成粉状、粘稠状或油状产物 [16][17][18][19] , 温 度、时间和溶剂等因素对聚合物结构有很大影响 [20][21][22] , 产物中同时存在环状结构和线型结构(主要为 1,4-和 3,4-结构) [23] . Gaylord 等 [24] 发现 TiCl 4 、AlCl 3 和 AlEtCl 2 等路 易斯酸在正庚烷中催化异戊二烯阳离子聚合转化率较 低, 聚合物以环状结构为主, 线状结构的含量一般不超 过 20%, 但在芳香族溶剂中反应速率更高, 且聚合物中 线性结构含量增大.…”

Expanding Monomers as Anti-Shrinkage Additives

“…The density of 1,3-butadiene (0.62 g·mol −1 ; no ring present) [ 8 ], cyclobutene (0.73 g·mol −1 ; 1 ring present) [ 9 ], bicyclo[2.2.2]oct-2-ene (0.91 g·mol −1 ; 2 rings present) [ 10 ], and tricyclo[4.2.0.0 2,5 ]octane (1.04 g·mol −1 ; 3 rings present) [ 11 ] increases alongside with the number of rings present in the molecular structure, indicative of a comparably dense atomic packing in the rings. Theoretical consideration of polymerizations of these “monomers” with the molecular formulae of (C 4 H 6 ) n (n = 1, 1, 2, 2) yielding poly(butadiene) with the molecular formula of (C 4 H 6 ) ∞ (density of 0.91 g·mol −1 ) [ 12 ] reveals that the polymerizations of 1,3-butadiene and cyclobutene would experience volumetric shrinkage, while the polymerization of bicyclo[2.2.2]oct-2-ene would proceed in volume-neutral fashion and only that of tricyclo[4.2.0.0 2,5 ]octane would show volumetric expansion.…”