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We describe the rational design of oligothiophene semiconductors to facilitate solution-based fabrication of environmentally stable organic field-effect transistors (OFETs). Ultrathin films of α,ω-distyryl quaterthiophene (DS4T), pentathiophene (DS5T), and sexithiophene (DS6T) were prepared via solution processing to probe the effect of styryl end groups, oligomer length, and thin film structure on air stability. These films were prepared via solution deposition and thermal annealing of precursors featuring thermally labile ester solubilizing groups. A detailed study of the thin film structure was performed using atomic force microscopy (AFM), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and grazing incidence X-ray diffraction (GIXD). Functional OFETs were obtained for DS5T and DS6T and have, respectively, hole mobilities of 0.051 and 0.043 cm2/(V s) and on/off ratios of 1 × 105 to 1 × 106, whereas DS4T OFETs failed to function because of poor film continuity. The effect of both short-...

Bipolar transport polymers have been developed as host materials for electroluminescent devices by incorporating both electron-transporting and hole-transporting functionalities into copolymers. Two different copolymers having the same molecular weight (Mn ∼ 30 kg/mol) and the same fraction of electron-transporting monomers (fOXA = 0.50) have been synthesized in the form of random and diblock copolymers, respectively. The effect of molecular structure and film morphology of these bipolar polymers on device performance has been studied. For the diblock copolymers, pronounced phase segregation forming different nanomorphologies has been observed by modern microscopic techniques, which is not observed for the random counterparts under the same thin film preparation conditions. The results of single-layer polymer light emitting diodes (PLEDs) show that the nanophase separation morphology of diblock copolymers has a significant effect on device performance: lowering charge transport and facilitating the hole−...

Hydrogen adsorption using a series of nanoporous synthetic polymers has been studied. Promising results were obtained during the screening of commercially available porous polymer beads; of the polymers considered, hypercrosslinked Hypersol-Macronet MN200 resin exhibited the highest adsorption capacity for hydrogen. This initial success triggered the development of our own high surface area hypercrosslinked materials. Subjecting gel-type and macroporous vinylbenzyl chloride-based precursors swollen in dichloroethane to a Friedel−Crafts reaction catalyzed by iron trichloride afforded beads with surface areas of 1 930 and 1 300 m2/g, respectively, as calculated using the BET equation. The former polymer reversibly stores up to 1.5 wt % H2 at a pressure of 0.12 MPa and a temperature of 77.3 K. The initial heat of adsorption of hydrogen molecules onto this polymer is 6.6 kJ/mol.

Symmetrical α,ω-substituted quarter-(T4), penta-(T5), sexi-(T6), and heptathiophene (T7) oligomers containing thermally removable aliphatic ester solubilizing groups were synthesized, and their UV−vis and thermal characteristics were compared. Spun-cast thin films of each oligomer were examined with atomic force microscopy and near-edge X-ray absorption fine structure spectroscopy to evaluate the ability of the material to self-assemble from a solution-based process while maintaining complete surface coverage. Films of the T5−T7 oligomers self-assemble into crystalline terraces after thermal annealing with higher temperatures required to affect this transformation as the size of the oligomers increases. A symmetrical α,ω-substituted sexithiophene (T6-acid) that reveals carboxylic acids after thermolysis was also prepared to evaluate the effect of the presence of hydrogen-bonding moieties. The charge transport properties for these materials evaluated in top-contact thin film transistor devices were found t...

The role of architecture and nanoenvironment in the catalytic properties of dendritic polymers containing 4-(dialkylamino)pyridines was investigated in the context of acylation reactions employing sterically demanding tertiary alcohols as substrates. Frechet-type benzyl ether and aliphatic ester dendrimers were prepared in a convergent manner from a common trivalent core containing three DMAP groups while a linear polymer was dendronized with aliphatic esters using a divergent growth scheme. Catalysis experiments clearly indicate that nanoenvironment plays the dominant role in determining the activity of the polymer catalysts, with the polyester platform being superior to the benzyl ether. Polymer architecture played little or no role in affecting catalysis. With respect to molecular transport and catalysis, this represents the first comparative study of the effect of architecture and nanoenvironment using structurally similar dendritic materials.

The highly compact and globular shape, as well as the uniform size and plurifunctionality of dendrimers make them ideal molecular building blocks for a wide range of interfacial materials involving self-assembled monolayers, Langmuir films, multilayers, and other surface-confined assemblies. Moreover, the study of the behavior of dendrimers at surfaces and interfaces provides unique insight into their chemical and physical properties. Dendritic macromolecules play an increasingly important role in the materials and surface sciences, where applications utilizing polymer thin films can benefit from their distinctive chemical and physical properties. Recent investigations have highlighted the use of dendrimers as functional surfaces and as interfacial materials for applications in membranes, adhesion, microelectronics or in chemical and biological sensing.

Natural photosynthetic systems collect sunlight using a vast array of light-harvesting chromophores that channel the absorbed energy to a single reaction center. Recently, it has been realized that dendritic macromolecules can exhibit similar properties, though on a more modest scale. The preparation of dendritic structures and assemblies composed of numerous light-collecting chromophores that transfer their energy to a single energy ‘sink’ at the core has been achieved in a number of diverse and creative ways. These novel structures are being used as model systems in light-emitting diodes, signal amplifiers, fluorescent sensors, frequency converters, and other photonic devices.

The thin film microstructure development of functionalized oligothiophenes with branched, thermally removable groups at each end of conjugated cores with five, six, and seven thiophene rings was monitored during their thermal conversion from solution processible precursors to insoluble semiconductor products. The change in end group character provides a comparison of branched vs linear end group functionalization in oligothiophenes. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy confirmed that branched alpha-, omega-substitutions of the precursors strongly influenced the packing of the conjugated core. The quinque- and sexithiophene precursors oriented perpendicular to the substrate, whereas the septithiophene precursor oriented parallel to the substrate, providing one of the first examples of length dependence in oligothiophene orientation. This dependence may be due to a packing mismatch between the conjugated cores and the branched end groups. The convertible septithiophene exhibits four distinct microstructures as it converts from precursor to product that correlate strongly with its field-effect hole mobility in field-effect transistors. The extent of septithiophene order and the surface-relative orientation of its ordered phases clearly influence field-effect transistor performance.

An acid catalysed rearrangement that transforms a bicyclic lactone into a phenolic carboxylic acid has been tested for potential use in chemically amplified microlithographic imaging.

A new class of porphyrin containing hyperbranched polymers has been prepared via proton-transfer polymerisation utilising an A2 + B3 approach, thus providing an accelerated entry into the construction of branched multiporphyrin architectures.

N-(p-methylstyryl)-(1R,2S)-ephedrine is prepared by alkylation of p-chloromethylstyrene under conditions which do not favor quaternization. A series of Copolymerization reactions confirm that the new chiral monomer and styrene copolymerize in random fashion with r1=1.09 and r2=0.98. The optical rotation of the copolymers does not vary linearly with composition. Applications of the copolymer include its use as chiral ligand for asymmetric synthesis or as a separation medium.

Dialkylaminopyridines whose N -substituents bear a hydroxyl or amino group can be made economically from 4-cyanopyridine. Simple but selective alkylation of these compounds with commercial (chloromethyl) or (3-bromopropyl) polystyrene gives several new solid-phase catalysts which are highly active in promoting the acylation of hindered alcohols. Comparison of syntheses and reactivities, among these and some other heterocyclic polymers, illustrates several useful general principles of reactive polymer chemistry such as local concentration and microenvironment effects.

The use of the t-BOC protecting group for the preparation of an organic soluble derivative of poly(vinyl alcohol) is reported. Poly(vinyl-t-butyl carbonate) can be obtained by free-radical polymerization of the monomer using peroxide or azo initiators at 90–120°C. The t-BOC polymer is thermolyzed cleanly to poly(vinyl alcohol) with evolution of carbon dioxide and 2-methyl-propene when heated to 210–220°C. The t-BOC polymer may be useful for imaging processes involving acid-catalyzed thermolysis.

The kinetics of phase-transfer catalysis using glycidyl methacrylate-ethylene dimethacrylate resins modified with pendant quaternary butylammonium groups have been studied. In contrast to expectations based on currently proposed mechanisms, the activity of polymeric catalysts is not improved through modifications that balance the hydrophilic and hydrophobic properties of the material. It is believed that much of the activity of the polymeric catalysts derives from the swelling of the polymer in both aqueous and organic phases. This enhances not only the rate of diffusion of both reagents to the vicinity of the catalytically active groups but also the ability of reactive groups to oscillate between the two phases. Both swelling and diffusion are restricted severely as the percentage of crosslinking is increased. This restriction is of particular importance with macroporous resins. Comparison of kinetic data obtained with various polymers suggests that gel polymers with very small bead sizes and therefore high external surface areas provide much higher reactivities than their macroporous counterparts.

Crosslinked polystyrene resins containing thiol or hydroxyl functionalities on a fraction of their aromatic rings were prepared by reaction of crosslinked polystyryllithium with elemental sulphur or oxygen followed by reduction of the resulting polymer. Similarly, resins containing hydroxymethyl or thiomethyl functional groups were prepared from chloromethylated polystyrene by displacement of chloride in procedures involving three phase systems and the use of a phase transfer catalyst. The degree of functionalization could be controlled easily and the sulphur containing polymers were free of disulphide bonds.

Several new reactive polymers containing various nitrogen functionalities have been prepared in bead form and tested as catalysts or ligands for reactive moieties in organic synthesis. In particular polymers containing 4-dialkylaminopyridine pendant groups show good to excellent catalytic activities depending on their structure and their microenvironment. Best results are obtained on polystyrene backbones when the catalytic species are removed from the styrene rings by a three carbon spacer. Poly-benzimidazole resins prepared by precipitation polymerization are good ligands for transition metal catalysts used in the catalytic hydrogenation of nitro compounds or olefinic double-bonds. The PBI resins can also be used to prepare a polymeric oxidizing reagent through the binding of Cr(VI); the reagent oxidizes alcohols to the corresponding carbonyls while spent Cr(II) or Cr(III) remains anchored to the polymer. Other polymers containing chiral amino-alcohol pendant groups show useful properties as chiral auxiliaries in the asymmetric reduction of ketones using polymer-complexed lithium aluminium hydride.

An efficient synthetic route to pure, high molecular weight poly(p-hydroxystyrene) is reported. The route involves synthesis of a new monomer, p-tert-butoxycarbonyloxystyrene, polymerization by radical initiation or by cationic initiation in liquid SO2, followed by thermolysis or acidolysis of the tert-butoxycarbonyl protecting group. Porous, crosslinked resin beads containing the nucleophilic, phenol pendant group have been prepared in a similar fashion from the precursor terpolymer of p-tert-butoxycarbonyloxystyrene, styrene and divinylbenzene. The utility of this resin for solid-phase synthesis has been demonstrated.

In this paper the design of radiation sensitive polymeric imaging systems is reviewed. Advances in design have led to systems that function on the basis of radiation‐induced changes in the polarity of polymer repeating units rather than cross‐linking. These new systems offer improved resolution, since they do not swell during development. Improvement in sensitivity has been achieved by designing systems that incorporate chemical amplification. The design principles leading to amplification and examples of systems that demonstrate amplification are presented.

Poly(methyl acrylate) was transformed into polymers containing α-substituted units by a two-step reaction sequence involving formation of a poly(enolate) by base abstraction of the hydrogens located α to the ester carbonyl groups, followed by reaction of the poly(enolate) with electrophiles such as carbon dioxide, sulfur dioxide, or ethyl bromoacetate. Further modification of the α-carboxylate or α-sulfinate polymers led to poly(acrylates) bearing α-methyl carboxylate, α-methyl sulfone, or α-(2-hydroxyethyl sulfone) functional groups. Quenching of the poly(enolate) with ethyl bromoacetate gave a polymer containing itaconate as well as acrylate units. In general, the degree of functionalization achieved was from 0.3 to 0.65.

A polymeric reagent, polystyryldiphenyl-phosphine tetrahydroborate copper, has been prepared by chemical modification of cross linked polystyrene using a fourstep reaction sequence involving a ligand exchange reaction for the binding of cuprous chloride to the phosphine resin. The reagent is very effective in the reduction of acid chlorides to aldehydes and can be regenerated easily without loss of activity.

Styrene polymers containing pendant p-vinyl or p-oxirane functionalities on some of their aromatic rings have been prepared in excellent yields by chemical modification of chloromethylated polystyrene or carboxaldehyde-substituted polystyrene under phase transfer catalysis. The polymers containing pendant vinyl groups were obtained by Wittig reactions with aqueous formaldehyde while the polymers with p-oxirane pendant groups were obtained by reaction of the carboxaldehyde polymer with trimethyl sulfonium chloride or epoxidation of the p-vinyl substituted polymer.

Sulfinate functional groups have been introduced on selected positions of the aromatic rings of soluble or crosslinked polystyrene via lithiation reactions followed by quenching with sulfur dioxide. The sulfinate polymers have good stability, can be stored at room temperature, and can be used for ion-exchange or as nucleophiles to produce polymer-bound sulfones. Good functional yields of polystyrene resins with sulfone pendant groups can be obtained by reaction of the polymeric sulfinates with various alkyl halides under phase transfer or classical conditions.

Polymers containing allylic and benzylic carbonate repeating units have been prepared by phase-transfer catalyzed polycondensation of activated bis-carbonates or carbamates and diols. The polymers are highly susceptible to thermal depolymerization and revert to small molecules when heated to temperatures which vary from 140 to 230°C depending on structure. The thermolysis temperatures are reduced to well below 100°C if catalytic amounts of acid are added to the polycarbonates. The thermolysis or acidolysis of bis allylic or benzylic carbonates provides a convenient route to aromatic compounds as demonstrated with both models and polymers. The polycarbonates can be used to formulate highly sensitive resist materials with potential for self-development of positive images. Some benzylic polycarbonates which produce polymerizable divinyl monomers upon thermolysis can be used to create negative images in a process which includes both depolymerization and photocrosslinking.