Synthesis and characterization of soft-hard stereoblock polybutadiene with Fe(2-EHA)₃ /Al(i -Bu)₃ /DEP catalyst system

Abstract

Stereoblock polybutadiene (PBD) composed of amorphous equibinary cis−1,4/1,2 PBD (e‐PBD, soft) and crystalline syndiotactic 1,2‐PBD (s‐1,2‐PBD, hard) segments is synthesized through one‐pot sequential polymerization with iron(III)2‐ethylhexanoate/triisobutylaluminum/diethyl phosphate [Fe(2‐EHA)3/Al(i‐Bu)3/DEP] catalyst system. The first‐stage polymerization of 1,3‐butadiene (BD) is carried out at a low [Al]/[Fe] ratio to give amorphous e‐PBD block, and sequentially, the in situ addition of excessive Al(i‐Bu)3 and BD to the living polymerization system give rise to a second crystalline s‐1,2‐PBD block. The length of each block is controllable by adjusting cocatalyst and monomer feed ratio. The syndiotactic pentad content is in the range of 63.8–76.6% and increases with the length of s‐1,2‐PBD block. The copolymer exhibits glass transition temperature (Tg) around −40 °C and melting point (Tm) around 168 °C originating from e‐PBD and s‐1,2‐PBD blocks, respectively. The incompatibility between s‐1,2‐PBD and e‐PBD blocks as well as the crystallization of s‐1,2‐PBD block induce the microphase separation in stereoblock PBD. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1182–1188

Polymerization of 1,3-butadiene catalyzed by a thermal robust, high selective and active iron catalyst: An applicable recipe for producing syndiotactic 1,2-polybutadiene

“…We have reported a series of phosphoryl derivatives assisted iron catalysts [32,33,46], and found that the catalytic performances for 1,3-butadiene polymerization largely depended on the nature of additive. Triarylphosphate is efficient additive for 1,2 selectivity, and incorporation of electron-withdrawal groups on the aryls benefits the activity but slightly decreases the selectivity, while bulky substituent is beneficial to the selectivity.…”

“…Recent discoveries have suggested that there may be a surprising advantage to using commercial available phospha(i)te as third component for improving both selectivity and activity, and thus has offered a range of potential industrially relevant catalyst components, which are more forgiving in terms of easy synthetic feasibility, cost and labour intensity, yet still deliver excellent control over the stereoregularity of the polymer with satisfied catalytic activity. Quest for such additives has advanced recently with development of dialkylphosphite, with which the iron catalyst produced 1,2-enriched polybutadiene possessing syndio arrangements (1,2-selectivity: 87e95%, pentad rrrr denoted syndiotactivity: 81e90%), atactic 1,2-polybutadiene (as elastomer, 1,2-: 55e87%) as well as their block copolymer and in-situ formed blend by controlling the activators feeding at industrially favored polymerization conditions [32,33,46,47]. These exceptional findings stimulated our interest in continuing innovation of potential additive for increasing the catalytic properties, e.g.…”

“…regio-and/or stereoselectivity of polydiene are of prime importance because these chemical structures are crucial to the resultant polymer properties. In particular, 1,3-butadiene is an attractive monomer and its stereospecific polymerization affords polybutadienes with diversified microstructures (i.e., 1,4-cis [1e9], 1,4-trans [10e21], 1,2-syndiotactic [22e31] and 1,2-atactic [32,33] as well as their combinations [32e34]. Following Natta's pioneering study in the 1960s [10], numerous metal catalysts have been exploited for the selective polymerization of 1,3-butadiene, especially cis-1,4 selective polymerization, whereas, 1,2-polymerization is less developed, probably due to the limited understanding of the catalysis process and catalyst structure-polymer properties relationship, although the product 1,2-polybutadiene, depending on the stereoregularity, have been used to manufacture tire, sole, preservative film as well as filler as reinforcing agent.…”

In-chain functionalized syndiotactic 1,2-polybutadiene by a Ziegler–Natta iron(iii) catalytic system

“…This result agrees with our previous research on Fe(III)-mediated 1,3-butadiene homopolymerization. 40 External phosphorous donors also signicantly inuenced the copolymerization performances. Increasing the P/Fe ratio from 1 to 10 rst led to the formation of sPB and then produced amorphous 1,2-PB rubber, this is consistent with our previous conclusion that higher P/Fe molar ratio favours the formation of amorphous 1,2-polybutadiene.…”

Synthesis of Stereodiblock Polybutadiene Using Cp*Nd(BH4)2(thf)2 as a Catalyst

“…Some synthetic examples of stereoblock polymers are reported using Ni [2], Co [3,4] and Fe [5] catalysts with additional ligands, or rare-earth metal catalysts with chain transfer reagent [6]. However, these stereoblock polymers always contain atactic blocks or short stereoregular blocks consist of less than 10 repeating units.…”