Heterofunctional Linking Agents for the Synthesis of Well-Defined Block Copolymers of Dimethylsiloxane andtert-Butyl Methacrylate or 2-Vinylpyridine

Abstract

The synthesis of block copolymers with a high degree of molecular and compositional homogeneity has facilitated researchers in understanding properties such as morphology, 1,2 dynamics, 3 adsorption, 4,5 and rheology. 6 Furthermore, block copolymers have found useful applications 7 and are potential candidates for many others. 8 The most powerful method for the synthesis of block copolymers is the sequential addition of monomers by anionic polymerization. Unfortunately, there are pairs of polymeric blocks, such as poly(dimethylsiloxane) (PDMS) and polymethacrylates (PMA), that cannot be prepared by this procedure, because the nucleophilicity of the living polymeric blocks does not match the electron affinity of the other monomer. To overcome this problem, Hogen-Esch et al. 9 prepared an -OH endcapped poly(methyl methacrylate) (PMMA) using an R-OH protected initiator. In a second step, the -OH group was transformed, after deprotection, to -OLi group and used to initiate the polymerization of hexamethylcyclotrisiloxane (D 3 ). Although the block copolymers prepared are well-defined, the weak point of this methodology is the instability of the -C-O-Si-group that connects the two blocks. Other methods have been reported for the synthesis of PDMS-b-PMA by combining anionic with group transfer, 10 atom transfer radical, 11 or free radical polymerization. 12 The above procedures (refs 10-12) lead to materials with high molecular and compositional polydispersity.An alternative and perhaps more versatile approach for the synthesis of block copolymers would be one that employs a linking agent with two different functional groups (heterofunctional linking agent). The reactivity of the two groups should be different toward dissimilar macroanions. On the basis of the greater reactivity of the -Si(Me) 2 -Cl than -Ph-CH 2 -Cl group toward silicon-oxygen nucleophiles, 13 we are proposing 2-(chloromethylphenyl)ethyldimethylchlorosilane (CMPDMS) as an efficient heterofunctional linking agent for the synthesis of well-defined block copolymers of PDMS and poly(tert-butyl methacrylate) (PTBMA) or poly(2-vinylpyridine) (P2VP).Experimental Section. a. Equipment and Materials. n-Butyllithium (1.6 M) in hexanes, hexamethylcyclotrisiloxane (D 3 ) (98%), 2-vinylpyridine (98%), tertbutyl methacrylate (99%), (CH 3 ) 3 SiCl (99%), benzene (99%), tetrahydrofuran (THF) (99%), CsI (99.999%), and LiCl (99%) were purchased from Aldrich. CMPDMS (98%), a mixture of para and meta isomers, was purchased from ABCR. Purification of monomers and solvents to the standards required for anionic polymerization has been described in detail elsewhere. 14 s-BuLi was prepared in vacuo from s-butyl chloride and lithium dispersion. Addition and removal of the reagents were performed using break-seals and constrictions. 14 CMPDMS was purified by fractional distillation under high vacuum (10 -6 Torr).Size exclusion chromatography (SEC) experiments were carried out at 25°C in two different setups. In the first a Waters model 510 pump, a Waters model 410 differential ...

Evaluation of siloxane and polyhedral silsesquioxane copolymers for 157 nm lithography

“…12 3-͑3,5,7,9,11,13,15-Heptacyclopentylpentacyclo ͓9.5.1.1 3,9 .1 5,15 .1 7,13 ͔ octasiloxane-1-yl͒ propyl methacrylate ͑cp-POSS͒ and 3-͑3,5,7,9,11,13,15-Heptaethylpentacyclo ͓9.5.1.1 3,9 .1 5,15 .1 7,13 ͔ octasiloxane-1-yl͒ propyl methacrylate ͑e-POSS͒ were purchased from Hybrid Plastics and were used as received. 12 3-͑3,5,7,9,11,13,15-Heptacyclopentylpentacyclo ͓9.5.1.1 3,9 .1 5,15 .1 7,13 ͔ octasiloxane-1-yl͒ propyl methacrylate ͑cp-POSS͒ and 3-͑3,5,7,9,11,13,15-Heptaethylpentacyclo ͓9.5.1.1 3,9 .1 5,15 .1 7,13 ͔ octasiloxane-1-yl͒ propyl methacrylate ͑e-POSS͒ were purchased from Hybrid Plastics and were used as received.…”

Synthesis and characterization of PS‐b‐PDMS‐b‐PS triblock copolymer

“…So many modification methods had been applied to improve mechanical performance of PDMS. [16][17][18][19][20] Recently, Sun and Liu 21 researched poly(methyl methacrylate) (PMMA)-b-PDMS-b-PMMA, which synthesized via activators generated by election transfer atom transfer radical polymerization (AGET ATRP). [4][5][6][7][8][9] Block copolymers offer an attractive route to generate new types of materials that possess excellent properties because of the large variety of structural arrangements they give rise by spontaneous self-assembly into a diversity of mesophases.…”

Precise Synthesis of New Triblock Co‐ and Terpolymers by a Methodology Combining Living Anionic Polymers with a Specially Designed Linking Reaction

“…Previously, Hadjichristidis and his coworkers reported a quite effective methodology for the synthesis of block polymers difficult to be obtained by sequential polymerization 32–35. In this methodology, they prepared 2‐(chloromethylphenyl)ethyldimethylchlorosilane of a new heterofunctional terminator having benzyl chloride (BnCl) and silyl chloride moieties.…”