Owen W. Webster's research while affiliated with Mercy Research & Development and other places

... These geometrical isomers can have the same molecular weight and branching properties, but a wide range of aspect ratios. The disperse nature of the aspect ratio of geometrical isomers can potentially lead to differences in solubility, and also a wide range in solid-state packing and physical properties [61]. Because of these factors, variables other than number averaged molecular weight and degree of branching are needed to differentiate between isomers while describing the status of a polymerization system. ...

... Recent advances in polymer synthesis have allowed for the preparation of a large variety of amphiphilic block copolymers. Controlled/living polymerization techniques, such as anionic, cationic, Atom Transfer Radical (ATRP), Nitroxide-Mediated Radical (NMRP), Reversible Addition Fragmentation Chain Transfer (RAFT), Group Transfer (GTP), Ring Opening (ROP) and coordination polymerization have been successfully employed towards this direction [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. The most commonly used water soluble polymer is undoubtably poly(ethylene oxide) (PEO). ...

... The GTP is a commercially viable method to produce poly(alkyl)methacrylates with narrow MWD at room temperature [118]. A large variety of up to 100 different methacrylates-many of them specialty monomers have been successfully polymerized to form polymers with narrow MWD [119,120]. Bandermann and co-workers [121,122] synthesized functional silyl ketene acetal and used it to prepare macromonomers. In this section, the GTP is discussed briefly with the relevance to its similarities with anionic polymerization. ...

... Among various nucleophilic anions such as fluoride [118], bifluoride [26,126,127], cyanide [128 -130], and various oxyanion salts [131,132], that can be used as catalyst, tris(piperidino)sulfonium bifluoride (TPSHF 2 ) is the most effective in producing narrow molecular weight acrylic polymers in THF. However, the relative efficiency of a catalyst strongly depends on the corresponding acidity (pK a value) of the carbon acids from which it is derived. ...

... [2] In contrast to main chain liquid crystalline polymers, SCLCP are easy to solubilise in common solvents at room temperature and their mesophase temperatures are relatively low (,ambient). [3] Owing to this, SCLCP have attracted a lot of attention from researchers around the world. The pioneering work of Finkelmann, Plate, and others resulted in the formation of SCLCP. ...

... The direct transfer of the pentacoordinated siliconate from a chain end to the incoming monomer's carbonyl group, named 'associative' mechanism was originally proposed by Webster and Sogah. Double-labeling experiments of Farnham and Sogah supported this mechanism [302], though several questions related to this mechanism remained unanswered [303][304][305][306][307][308]. Kinetic experiments enabled Mai and Mu¨ller [291,298,309] to propose a modified two-stage associative mechanism in which the monomer adds to the a-carbon of pentacoordinated siliconate chain end and subsequently silyl group migration takes place to the carbonyl oxygen of the monomer (Scheme 23, center). ...

... Recently, Webster [25] has published results on the anionic polymerization of MMA with potassium dimethyl 2-methylmalonate/ 18-crown-6 in the presence of Table 3. The rate of polymerization was retarded and the molecular weight was lowered and determined by the monomer/malonate ratio. ...

... The reaction of water (from moisture or present as a trace impurity in the reagents) with hemiacetal ester probably led to the formation of the constitutive acid and an unstable 1-butoxyethan-1-ol hemiacetal (Scheme 2a), which readily dissociates into acetaldehyde and butan-1-ol. Butan-1-ol can then react with another hemiacetal ester (Scheme 2b) to form 1-(1-butoxyethoxy)butane. However, the reaction of vinyl ether with water to form acetaldehyde and alcohol, followed by reaction of the alcohol with another vinyl ether, was also reported [29] and this could be another pathway to the side products. Scheme 1. Acid-catalyzed reaction between carboxylic acids and vinyl ether leading to hemiacetal ester. ...

... Polymer chemistry has witnessed a real explosion over recent decades. A variety of living/controlled polymerization techniques have emerged over the years, which allows for the synthesis of macromolecules with controlled molecular weights, molecular weight distributions, stereochemistry, end-group functionalization, optical properties, etc. [1][2][3][4][5][6][7][8][9][10]. The employment of novel catalysts, linking, termination, and transfer agents, along with the use of recent advances in organic chemistry, e.g., Suzuki coupling, click chemistry, photochemical reactions etc., have led to the synthesis of complex well-defined macromolecular architectures [11][12][13]. ...

... On the contrary, hyperbranched polymers are synthesized in one step process to bring about a mixture of linearly and fully branched AB repeating units. In as such, the as synthesized polymeric product is supposed to acquire properties similar to those of dendreimers polymers (Kim and Webster 1999). Thus highly branched materials find increasing industrial interest in a way that they are considered to be a good alternative to dendriemers. ...