Marcus J. Caulfield

Studies on microgels. 5. Synthesis of microgels via living free radical polymerisation

Statistical and star microgels of t-butylstyrene-1,4-divinylbenzene (TBS-DVB) have been synthesized via living free radical polymerization using tetramethylpiperidin-1-oxyl (TEMPO) as a trapping agent. The alkoxyamines 1 and 2 were used as initiators to prepare statistical and star microgels, respectively. The molecular weight of the resulting microgels was determined by size exclusion chromatography with an on-line multi-angle laser light scattering (MALLS) instrument. It has been found that living free radical polymerization provides a much better control over the formation of statistical microgels than traditional free radical polymerization and can be used successfully for the synthesis of star microgels.

Degradation on polyacrylamides. Part II. Polyacrylamide gels

Abstract The stability of polyacrylamide (PAAm) gels, synthesized by free radical polymerization of acrylamide (AAm) and N , N ′-methylenebisacrylamide (BIS), was investigated when subjected to thermal and irradiation conditions. The PAAm gels were stable and did not release AAm under fluorescent light. In aqueous solution at 95 °C, a small amount of AAm was observed and it is shown that this is found from the pendant unsaturation of BIS in the gel network. Under UV irradiation, approximately one molecule of AAm is released for every 20,000 repeat monomer units in the gel. Gels were also synthesized from methacrylamide with BIS, AAm with N , N ′-methylenebismethacrylamide and AAm with bisacryloyl-piperazine. Their stability is compared to the AAm/BIS gels.

Studies on polyimides : 2. Formation of high molecular weight poly(N-(hydroxyphenyl) maleimides)

A series of N-(substituted phenyl) maleimides was synthesized and their free radical chain polymerization examined. Polymerization of the N-(hydroxyphenyl) maleimides in DMF gave typically very low molecular weight polymers. Masking the phenolic functionality with an acetoxy group gave marginally higher molecular weights. Protection using a tetrahydropyranyl (THP) substituent gave a similar polymerization pattern to acetoxy. However, the THP protected monomers had increased solubility in non-polar solvents such as benzene, and when polymerized in this solvent gave very much higher molecular weight polymers. The reactivity of the maleimide monomers was also found to be dependent on the substitution pattern of the phenyl ring, with substituents in the ortho position tending to lower the molecular weight of the polymer formed. The THP substituent was readily removed to yield poly(N-(hydroxyphenyl) maleimides). The polymers were found to exhibit excellent thermal stability.

Controlled Synthesis of Novel Dibenzene-1,2-diol Mannich Bases

The synthesis of a number of novel dibenzene-1,2-diol Mannich bases can be achieved in good yields by the condensation of 2-methoxyphenol, formaldehyde and secondary diamines. The newly developed synthetic method uti lizes 2-methoxyphenol instead of benzene-1,2-diol providing a useful tool for greater control over reaction products.

Studies on polyimides. Part 1: Synthesis of model compounds and their reaction with hexamethylenetetramine

The synthesis of a series of N-(hydroxyphenyl) succinimides is described along with their reaction with HMTA. The succinimides serve as a model for the more complicated polyimide/HMTA systems. Both benzoxazine and benzylamine type intermediates have been identified as the initial major intermediates formed depending on the substitution pattern of the phenolic ring. The rate of reaction of HMTA with the N-(hydroxyphenyl) succinimide compounds was measured via 13C nuclear magnetic resonance spectroscopy. It was found that the presence of the succinimide ring increases the reactivity to HMTA of the hydroxyphenyl compounds studied.

Novel cross-linked polyacrylamide matrices: an investigation using gradient gel electrophoresis.

Gradient gel electrophoresis was used to examine the separation properties of novel cross‐linking compounds for polyacrylamide (PAAm). At low %T and at the same %C protein migration difference is accentuated for bismethacrylamidc cross‐linked networks relative to bisacrylamide cross‐linked networks. Similar properties were observed for cyclic monomers at low %T. This trend is maintained throughout the gradient. However, at higher %T migration differential relative to N,N′‐methylenebisacrylamide (Bis) was less pronounced. Evidence from gradient gels suggests that reactivity and functionality of vinyl groups impose an overriding control over network formation.

Complexes of Benzene-1,2-diol Mannich Bases. I. Novel Hexacoordinate Zwitterionic Silicon(IV) Complexes

This paper reports the synthesis and characterization of a number of novel silicon(IV) complexes with a range of mono-Mannich bases of benzene-1,2-diol. Mannich bases of general structure 3-(dialkylaminomethyl)benzene-1,2-diol form zwitterionic 6-coordinate tris complexes with silicon(IV), eliminating the need for an external counter ion. These complexes exhibit marked differences in their ability to partition between an aqueous and organic phase compared with the analogous tris(benzene-1,2-diol) silicon(IV) complex. Mannich bases of diamines and benzene-1,2-diol will also complex to silicon; however, they result in more complicated polymeric structures.

Complexes of Benzene-1,2-diol Mannich Bases. II. Novel Aluminium(III) Complexes

Benzene-1,2-diol readily forms complexes with aluminium(III) ions, under anhydrous conditions, to give a mixture of mononuclear and polynuclear entities. These complexes are anionic and require external counter ions to achieve electrical neutrality. Mannich base derivatives of benzene-1,2-diol (that is 3-(dialkylaminomethyl)benzene-1,2-diols) form similar mononuclear and polynuclear complexes but these are self neutralizing (eliminating the need for external counter ions) and are best described as zwitterionic. These complexes exhibit significant differences in their ability to partition between an aqueous and organic phase using a range of organic solvents.

Control of reactivity of novolac resins: the use of 3,4-dihydro-2H-pyran as a labile protecting group

The control of the reactivity of novolac resins towards common crosslinkers through the use of 3,4-dihydro-2H-pyran as a protecting group is reported. This thermally labile protecting group is shown to be effective for the control of the cure of the novolac resin system through the use of models and on the resins themselves. The option of controlling the temperature of cure of the resins through the manipulation of the pH of the reaction mixture is also reported. The control of the cure was measured by differential scanning calorimetry (DSC). The use of the protecting group as a means to manipulate the structure of the cured resins is discussed.