Recent advances in the synthesis of block, graft and star polymers containing inorganic macromolecular species are described. Anionic copolymerization techniques were used in the formation of diblock copolymers of poly(styreneblock-methylphenylsilylene) and poly(isopreneblock-methylphenylsilylene) by the ring-opening polymerization of 1,2,3,4-tetramethyl-1,2,3,4tetraphenylcyclotetrasilane initiated by living anionic polystyrene and isoprene respectively. Hydrosilation of an attachable initiator onto telechelic vinyl-or hydrosilyl-terminal or-pendant poly(dimethylsiloxane) (PDMS) yielded a PDMS macroinitiator. This macroinitiator was used in atom transfer radical polymerization (ATRP) of styrene and isobornyl acrylate to produce ABA triblock copolymers. As a model for graft copolymers from a polyphosphazene backbone, chemical transformation of hexachlorocyclotriphosphazene resulted in hexafunctional molecules containing either benzyl bromide or bromopropionyl moieties. The initiator 1,1,3,3,5,5-hexakis[4-(2bromopropionyloxymethyl)phenoxy]cyclotriphosphazene was used in the ATRP of styrene to yield a polymer with a narrow, monomodal molecular weight distribution. Chain extension of this star polymer with isobornyl acrylate is also described.

Novel poly(methylphenylsilane)-poly(ferrocenyldimethylsilane) copolymers 5a-d of varying monomer composition were prepared via the thermal ring-opening polymerization of a mixture of the strained cyclic tetrasilane [MePhSi]4 (1) and the silicon-bridged [1]ferrocenophane Fe(η-C5H4)2SiMe2 (3). The resulting materials were structurally characterized by 1 H and 29 Si NMR and also by gel permeation chromatography (GPC), pyrolysis mass spectrometry (MS), and cyclic voltammetry. GPC in THF indicated that the molecular weights of the polymers 5a-d were in the range Mn ) (2.0 × 10 4 )-(8.9 × 10 4 ) with PDI values of 2.4-3.5. Polymers 5a-c were photosensitive and GPC traces of 5a-c were studied both before and after irradiation of the sample with UV light (λ ) 340 nm). The formation of short chain oligo(ferrocenylsilanes) after irradiation was consistent with exclusive photodegradation of the polysilane segments and indicated that the copolymers were random in nature. Pyrolysis MS of 5a-c also supported a random structure. Cyclic voltammetric studies of 5a-c in CH2Cl2 showed the presence of the characteristic two reversible oxidation waves arising from oligo(ferrocenylsilane) segments with interacting iron atoms at E1/2 ) 0.00 and 0.23 V (relative to ferrocene/ferrocenium) and an irreversible oxidation with Ep(ox) ) 0.39 V arising from the polysilane segments. UV/vis spectroscopy showed that the σ-electrons in the oligosilane segments are delocalized and that λmax increased from 325 to 333 nm as the proportion of the cyclotetrasilane 1 in the initial monomer mixture increased. These values suggest that the oligosilane segments are relatively short and do not approach the limit corresponding to ca. 30 silicon atoms (Mn ) ca. 3 000), which levels off at 338 nm. Attempted anionic initiation of the copolymerization of 1 and 3 was unsuccessful and led exclusively to homopolymerization. Transition metal catalyzed copolymerization of 1 and 3 using PtCl2 resulted in a copolymer which was derived almost exclusively from 3. The charge transport properties of the representative copolymer 5d were also investigated. Films of pristine 5d were insulating (conductivity <10 -14 S cm -1 ) but after exposure to iodine the conductivity increased by a factor of 10 8 to (6.5-8.2) × 10 -6 S cm -1 . In comparison, the conductivities of iodineexposed films of poly(ferrocenyldimethylsilane) (4) and poly(ferrocenyldi-n-butylsilane) (7) were ca. 2 × 10 -4 S cm -1 . The hole mobility of 5d was studied by standard time of flight techniques and was found to be appreciable with a value of 4.0 × 10 -6 cm 2 /V s.

Synthesis of hyperbranched poly(arylene ether phosphine oxide)s, HB PAEPOs, from bis(4-fluorophenyl)(4-hydroxyphenyl)phosphine oxide, 1a, in the presence of a series of core molecules with systematically altered reactivity of the aryl fluoride groups provides polymers with molecular weights, MWs, controlled by the concentration of the core molecule, and narrow polydispersity indices, PDIs. Polymers with number-average molecular weights ranging from 3270 to 8100 Da, and PDIs as low as 1.25 have been prepared. The core molecules utilized in this work consist of a series of fluorinated triarylphosphine oxides, tris(4-fluorophenyl)phosphine oxide, tris(3,4-difluorophenyl)phosphine oxide, and tris(3,4,5-trifluorophenyl)phosphine oxide, 2a, 2b, and 2c, respectively. The most highly activated core, 2c, provides the best control over the final MW and the lowest PDIs. The degree of branching, DB, for the HB PAEPOs decreases from 0.57 with no core to below 0.40 at higher concentrations of 2b and 2c.

A series of ABx‐type triarylphosphine oxide monomers, bis‐(4‐fluorophenyl)‐(4‐hydroxyphenyl)phosphine oxide (4a), bis‐(3,4‐difluorophenyl)‐(4‐hydroxyphenyl)phosphine oxide (4b), and 4‐hydroxyphenyl‐bis‐(3,4,5‐trifluorophenyl)phosphine oxide (4c) were prepared, characterized, and polymerized under nucleophilic aromatic substitution conditions [N‐methylpyrrolidone (NMP), K2CO3] to provide the corresponding hyperbranched poly(arylene ether phosphine oxide)s with number‐average molecular weights ranging from 9200 to 14,600 Da. NMR spectroscopic analysis indicated the presence of highly branched products with an approximate degree of branching of 0.57. The polymers were soluble in a variety of typical organic solvents and displayed excellent thermal stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1456–1467, 2002

A series of hyperbranched poly(arylene ether phosphine oxide)s (HB PAEPOs) were prepared via an A 2 ϩ B 3 polymerization scheme with tris(4-fluorophenyl)phosphine oxide as B 3 , and a variety of bisphenols as A 2 . The effects of the reactivity of the A 2 monomer, the A:B ratio, the addition mode, the solvent, and the concentration on the final molecular weight, polydispersity index (PDI), and degree of branching (DB) were studied. Soluble HB PAEPOs with weight-average molecular weights of up to 299,000 Da were achieved. Reactions in which the A 2 component was added slowly resulted in lower DBs (0.2-0.5), whereas the slow addition of the B 3 component provided samples with DBs of approximately 0.75. Reactions performed under highdilution conditions afforded completely soluble materials with weight-average molecular weights of 9000 -12,100 Da and PDI values as low as 2.20. The molecular weights achieved under high-dilution conditions were independent of the mode of monomer addition.