Cationic Graft Polymerization from Ultrafine Silica Initiated by Acylium Perchlorate Groups Introduced onto the Surface

Abstract

ABSTRACT:The introduction of acylium perchlorate groups onto ultrafine silica was achieved by the reaction of silver perchlorate with acyl chloride groups, which were introduced by the treatment of carboxyl groups with thionyl chloride. The introduction of carboxyl groups onto silica surface was achieved by the hydrolysis of acid anhydride groups which introduced by the treatment of silica with 4-trimethoxysilyl tetrahydrophthalic anhydride. Surface acylium perchlorate groups introudced onto silica were capable of initiating cationic polymerization of styrene and polystyrene was effectively grafted onto the surface. The percentage of grafting increased to 65.4%. The grafting efficiency was high during the first few conversion but rapidly decreased with an increase in conversion. This suggests that the grafted polymer propagates from acylium perchlorate groups and that un grafted polymer is gradually formed by a chain transfer of growing polymer cation to the monomer. The cationic ring-opening polymerizations of tetrahydrofuran, styrene oxide, j'i-propiolactone, and e-caprolactone were also initiated by acylium perchlorate groups on silica surface to give the corresponding polymer-grafted silica. The polymer-grafted silica gave a stable colloidal dispersion in good solvents for grafted polymer.

Branched Polymer-Grafted Silica. Cationic Postgrafting from Pendant Acylium Perchlorate Groups of Grafted Polymer Chains on Ultrafine Silica Surface

“…The percentages of postgrafting and overall grafting at 60°C after 24 h reached 80 and 120%, respectively. As previously reported, the percentages of grafting of polystyrene in the polymerizations initiated by azo, 3 peroxide,4 and acylium perchlorate 6 groups on the silica surface reached 16.2, 3 25.0, 4 and 64.5%, 6 respectively. Moreover, the percentage of postgrafting of polystyrene in radical postgrafting to unsaturated polyester chains previously grafted onto carbon black surface increased to about 40%.…”

“…14 We reported the introduction of acylium perchlorate groups onto carbon black and silica surfaces. These acylium perchlorate groups were capable of initiating the cationic graft polymerization of vinyl monomers, 6 • 15 and the cationic ring-opening polymerization of lactones, 6 • 16 cyclic ethers, 6 • 17 • 18 and cyclic acetals 19 to give the corresponding polymergrafted carbon black. Accordingly, it is expected that the pendant acyl chloride groups of poly(styrene-co-AC) chains grafted onto the silica surface react with silver perchlorate to give pendant acylium perchlorate groups which have initiating activity for the cationic postgraft polymerization.…”

“…For instance, acylium perchlorate groups introduced onto a silica surface have ability to initiate the cationic polymerization of vinyl monomers and the cationic ringopening polymerization of lactones and cyclic ethers to give the corresponding polymergrafted ultrafine silica. 6 On the other hand, the dispersibility and the wettability of these ultrafine particles are influenced by the percentage of ! ):rafting of polymers because the grafted polymer chains on the surface interfere with the aggregation of the particles and increase the affinity of the surface for solvents.…”

Surface Graft Polymerization of Styrene onto Nano-Sized Silica with a One-Pot Method

“…Peroxide groups, 6, 7 azo groups [8][9][10] and redox initiators 11 had been introduced onto the surface of nano-sized silica for the free radical polymerization of styrene and methyl methacrylate. Acylium perchlorate groups 12 had been immobilized onto the surface of the nano-sized silica for the cationic polymerization of styrene, cyclic ethers and lactone. Styrene, [13][14][15][16] methyl methacrylate 13 and butyl methacrylate 17 had been initiated for the atom transfer radical polymerization (ATRP) on the surface of the nano-sized silica.…”

Curing of Epoxy Resin by Hyperbranched Poly(amidoamine)-grafted Silica Nanoparticles and Their Properties

“…By grafting of functional polymers onto the surfaces, nanoparticles may be endowed with special functions such as photosensitivity, bioactivity, crosslinking ability, and amphiphilic properties. [1][2][3][4][5] We have reported the surface initiated graft polymerization of various monomers onto silica nanoparticle by using previously introduced initiating groups on the surface, such as azo 6 and peroxyester, 7 acylium perchlorate, 8 and potassium carboxylate. 9 In addition, we have reported that hyperbranched poly-(amidoamine) (PAMAM) can be grown from amino groups on silica nanoparticles, 10 chitosan powder, 11 and carbon black 12 surfaces using dendrimer synthesis methodology ( Figure 1).…”