Sequence Determination and Regulation in the Living Anionic Copolymerization of Styrene and 1,1‐Diphenylethylene (DPE) Derivatives

Abstract

The living anionic copolymerization of styrene (St) and 1,1‐diphenylethylene (DPE) derivatives were carried out to investigate how the DPE units are distributed along the polymer chain. Based on the combination of timing sample method and exact characterizations, the sequence determination method was established to reveal the sequential distribution of DPE units along the functionalized chains. In the copolymerization of St and DPE‐SiH, when DPE‐SiH was excessively fed, a strictly alternating structure can be prepared. As the feed ratios of S/D increased, a gradient structure was obtained. Additionally, when the substituent structure of the DPE derivatives changed, the sequence structure could be regulated. It has been confirmed in the copolymerization of St and DPE‐SiH/OMe or DPE‐SiH/NMe2, that the electron‐donating group (‐OMe or ‐NMe2) was introduced into DPE‐SiH. Then, the preliminary sequence regulation method was found. Meanwhile the sequence‐determined grafting was investigated, and bottlebrush polymers with sequence‐determined branches were successfully synthesized.

Sequence Features of Sequence-Controlled Polymers Synthesized by 1,1-Diphenylethylene Derivatives with Similar Reactivity during Living Anionic Polymerization

“…Especially in the sequence-controlled polymers synthesized by LAP with DPE derivatives, the number of interval units (such as St) sandwiched in between adjacent DPE units was regulated and calculated as average values. The precision of the statistical sequence structure in the same DPE derivative with different sequences, or the same sequence but different DPE derivatives, has become a critical problem for us when we explored plentiful sequence-controlled polymers with abundant DPE derivatives. ,,,,, The simulation of copolymerization with the kinetic Monte Carlo model (KMC), which is based on the exact stochastic simulation algorithm developed by Gillespie, , has been widely used to interpret detailed chain propagation, and proximate results have been reported. , Additionally, the “sequence equivalence” principle, as raised above, gives the possibility for us to carry out the simulation of kinetic propagation with the KMC model. Thus, in order to reveal the explicit sequence structure in copolymerization of DPE-heptyl and St, and to further estimate whether the KMC model is universal for LAP systems of DPE derivatives and St, we developed the corresponding KMC program based on the elementary reactions of the living anionic polymerization of DPE derivatives and St (Scheme ).…”

“…Tetrahydrofuran (THF) was dried by reflux over a Na–benzophenone and then distilled. Benzene (Certified ACS, EM Science), benzene- d 6 (Aladdin, 99.5%) and styrene (Aldrich, 99%) were purified as previously described …”

“…The special features exhibited by LAP impel totally different methods to synthesize the sequence-controlled polymers. What we should do is to explore ample methods to precisely and conveniently regulate the sequence structure for LAP. ,, The regulation of r St is a very important path for the sequence regulation during living anionic copolymerization of St and DPE derivatives. Different r St resulted in different sequence distributions of functional DPE units and multivariate properties for postfunctionalized polymers .…”

“…Second, the crossover reaction (i.e., k DS ≪ k SS and k SD ) existed and remarkably affected the copolymerization, which can lead to a relatively broad molecular weight distribution, especially for nonalternating copolymerization; thus, the precise control of the number of interval St units at low values (DPS-betw-D lower than 10) is almost impossible to achieve with the staged end-capping strategy. On the basis of these two notable disadvantages, we attempted a different approach to determine the sequence distribution of DPE units in polymer chains during one-pot copolymerization and regulate the sequence structure with varying the r St of DPE derivatives, 34 rather than the known sequential addition strategydif ferent methods and dif ferent paths, but the same purpose! The special features exhibited by LAP impel totally different methods to synthesize the sequence-controlled polymers.…”

Study on the Mechanism of a Side Coupling Reaction during the Living Anionic Copolymerization of Styrene and 1-(Ethoxydimethylsilyphenyl)-1-phenylethylene (DPE-SiOEt)

“…In addition, the sterically bulky DPE structure cannot be homopolymerized by any mechanism, except under extreme conditions [ 25 ]. Therefore, DPE derivatives have been used as co-monomers to regulate the polymer sequence through kinetic control [ 26 , 27 , 28 ].…”