The technique used to align liquid crystals-rubbing the surface of a substrate on which a liquid crystal is subsequently deposited-has been perfected by the multibillion-dollar liquid-crystal display industry. However, it is widely recognized that a non-contact alignment technique would be highly desirable for future generations of large, high-resolution liquid-crystal displays. A number of alternative alignment techniques have been reported, but none of these have so far been implemented in large-scale manufacturing. Here, we report a non-contact alignment process, which uses low-energy ion beams impinging at a glancing angle on amorphous inorganic films, such as diamond-like carbon. Using this approach, we have produced both laptop and desktop displays in pilot-line manufacturing, and found that displays of higher quality and reliability could be made at a lower cost than the rubbing technique. The mechanism of alignment is explained by adopting a random network model of atomic arrangement in the inorganic films. Order is induced by exposure to an ion beam because unfavourably oriented rings of atoms are selectively destroyed. The planes of the remaining rings are predominantly parallel to the direction of the ion beam.

Atom transfer radical polymerization (ATRP) of n-butyl acrylate with the homogeneous catalyst, CuIBr/4,4‘-di(5-nonyl)-2,2‘-bipyridine (dNbpy), in benzene, afforded well-defined poly(n-butyl acrylate) with predetermined molecular weights and low polydispersities, M w/M n = 1.1. The number-average molecular weight, M n (measured by GPC and MALDI-TOFMS), was close to the theoretical molecular weight, predetermined by DPn = Δ[M]/[I]0. A similar polymerization in benzene using 2,2‘-bipyridine (bpy) as ligand instead of dNbpy displayed poor control, yielding a polymer whose molecular weight was higher than the theoretical value and demonstrating high polydispersity (M w/M n = 2.4). Several solvents were subsequently employed for the polymerizations with the CuIBr/bpy catalyst system. Good control of molecular weight and polydispersity were achieved using ethylene carbonate, and in this system the observed rate of polymerization was even faster than in bulk. The rate of polymerization with the CuIBr/bpy catalyst in ethylene carbonate was first order with respect to the catalyst concentration; a reduction in the concentration of the catalyst led to an increase in the polydispersity of the resulting polymer. Polydispersity decreased on addition of CuIIBr2 or by reducing the amount of ethylene carbonate used. The polymerization in ethylene carbonate with CuPF6/bpy catalyst gave results similar to those observed for the CuIBr/bpy catalyst system. The rapid rate of polymerization in ethylene carbonate was attributed to a monomeric structure of the CuIBr/bpy catalyst, as found for CuIPF6.

Mono and difunctional polystyrenes containing active halogenated end groups were prepared by atom transfer radical polymerization (ATRP). Substitution reactions were explored to convert the halogen termini to azido groups, followed by reduction to form the amino functional polymer. Quantitative conversion of the end groups was observed in each transformation reaction. 'H NMR demonstrated the formation of the azide from the bromide functionality without elimination. The difunctional a,o-diaminopolystyrene was reacted with terephthaloyl chloride in a condensation process to produce chain-extended polystyrene containing amide bonds along the polymer backbone.

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.

No abstract