Tapered copolymers of styrene and 4‐vinylbenzocyclobutene via carbanionic polymerization for crosslinkable polymer films

Abstract

Well‐defined polystyrene homopolymers with surface‐adhesive triethoxysilyl end group were synthesized via living carbanionic polymerization, epoxide end‐functionalization and subsequent hydrosilylation with triethoxysilane. Grafting‐to performance of polymers with various molecular weight (Mn = 3000–14,000 g mol−1) to a silicon surface was examined in dependence of reaction time, polymer concentration, solvent and number of alkoxysilyl end groups. Crosslinkable polymers for surface modification were synthesized by statistical carbanionic copolymerization of 4‐vinylbenzocyclobutene (4‐VBCB) and styrene, followed by epoxide end‐functionalization and triethoxysilane modification (Mn = 4000–14,000 g mol−1). The copolymers were characterized by 1H‐NMR, THF‐SEC, and matrix‐assisted laser desorption and ionization time‐of‐flight mass spectrometry. In situ 1H‐NMR kinetic studies in cyclohexane‐d12 provided information regarding the monomer gradient in the polymer chains, with styrene being the more reactive monomer (rs = 2.75, r4‐VBCB = 0.23). Thin polymer films on silicon wafers were prepared by grafting‐to surface modification under conditions derived for the polystyrene homopolymer. The traceless, thermally induced crosslinking reaction of the benzocyclobutene units was studied by DSC in bulk as well as in 3–6 nm thick polymer films. Crosslinked films were analyzed by atomic force microscopy, ellipsometry, and nanoindentation, showing smooth polymer films with an increased modulus. © 2019 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 181–192

Tetrahydrofuran: More than a “Randomizer” in the Living Anionic Copolymerization of Styrene and Isoprene: Kinetics, Microstructures, Morphologies, and Mechanical Properties

“…Increase of the polymerization temperature can lead to a certain flattening of the gradient, which, however, may not be large enough . In contrast, changes in the gradient caused by variation of the monomers are larger (e.g., by using alkyl styrene derivatives and/or other 1,3-dienes), ,,,− albeit also affect other parameters considerably (e.g., χ AB , entanglement molecular weights, and thermal stabilities). , …”

In Situ Formation of Silica Nanoparticles Decorated with Well-Defined Homopolymers and Block Copolymers

“…Frey and co-workers 54 synthesized well-defined PS homopolymers with surface-adhesive double triethoxysilyl end groups via living carbanionic polymerization, epoxide end functionalization, and subsequent hydrosilylation with triethoxysilane and grafted on silicon wafers. However, our synthetic procedure uses fewer synthetic steps, and the termination step occurs without the addition of a catalyst.…”

Investigation of eight-arm tapered star copolymers prepared by anionic copolymerization and coupling reaction

“…As previously reported, 12,15,20–23 it is well-known that the direct statistical copolymerization of Ip and St in nonpolar hydrocarbons is a typical example to obtain the block-like polymer structure that was later denoted as a “tapered” copolymer to indicate the strong gradient of monomer units in the polymer structure. The tapered system has been recently extended to several monomer pairs including Ip/4-methylstyrene, 14,16 Ip/ p -alkylstyrene, 24 St/4-vinylbenzo cyclobutene, 25 St/β-farnesene, 26 St/β-myrcene, 27,60 and St(Ip)/4-trimethylsilylstyrene. 61 However, at present, the tapered star copolymers are rarely studied except for only two examples of the four-arm star.…”

“…To date, several approaches have been proposed to control the gradient composition in tapered copolymers depending on the reactivity ratios of monomers: (i) the addition of polar additives, 20,21 (ii) the injection of monomers with automated syringe pumps, 22 (iii) sequential addition of pure monomers or monomer mixtures, 23 and (iv) the use of substituted monomers. 15,24–27 However, at present, the tapered copolymers under study are mostly linear. Besides a four-arm tapered star copolymer system developed by Frey and coworkers, 28,29 there is rarely any report on a multi-arm tapered star copolymer.…”