Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Water-borne coatings often contain multiple additives including pigments, dispersing agents,
rheology modifiers, UV stabilizers and biocides. Due to their low molar mass and endocrinedisrupting
properties, many of these additives, upon leaching from the substrate film, with time
pollute water systems and become hazardous to the environment and to human health. In this study,
I aimed to develop a facile method for the production of a polymeric biocide to serve as alternative
to low molar mass biocides used in water-borne coatings. A secondary aim was to show that,
without additional modification, the polymeric species can be used in surfactant-free ab initio
emulsion polymerizations.
Using a two-step process, I modified a commercially available copolymer, poly(styrene-alt-maleic
anhydride) (SMA 1000), with mixed amines in order to obtain latexes with inherent antimicrobial
activity. In the first step, I reacted SMA 1000 with 3-dimethylamino-1-propylamine and aqueous
ammonia to confer antimicrobial activity and water-solubility to the SMA copolymer. In the second
step, the copolymer was incorporated into a film-forming styrene-butyl acrylate (STY/BuA) latex.
The modified SMA was incorporated into a latex in two ways: (1) post-added to the latex, and (2)
used as stabilizer in emulsion polymerization. In both cases, the latex remained stable for up to 11
months, and stability was probably due to steric stabilization of the polymer particles. Antimicrobial
activity of the latex film was achieved with both methods. When the modified SMA was post-added,
antimicrobial activity was restricted to specific areas on the eventual polymer film, and when
modified SMA was used as stabilizer, antimicrobial activity was evenly distributed throughout the
polymer film.
Fluorescence microscopy showed homogeneous distribution of antimicrobial activity upon
inoculation in Gram positive bacteria dispersions when the modified copolymer was used as
polymeric stabilizer for the synthesis of STY/BuA latexes. No antimicrobial activity against Gram
negative bacteria was achieved. The homogeneous distribution of antimicrobial activity throughout
the film was a result of adsorption of polymeric biocide/stabilizer to each individual latex particle.
With further commercial development, high molar mass copolymers modified for antimicrobial
activity may be a feasible, environmentally-friendly and healthy alternative to be used as stabilizers
in emulsion polymerizations to produce water-borne coatings. / AFRIKAANSE OPSOMMING: Waterverf bestaan gewoonlik uit ‘n verskeidenheid bestandele, onder andere: pigmente,
verspreiding middels, reologie modifiseerders, UV stabiliseerders en biologies aktiewe verbindings.
As gevolg van die lae molêre massa en die endokrien ontwrigtende vermoë van baie van die
bestandele hou hulle ‘n bedreiging in vir die omgewing in terme van waterbesoedeling en menslike
gesondheid, soos hulle die film oor tyd verlaat. In hierdie studie het ek beoog om ‘n eenvoudige
metode vir die vervaardiging van ‘n polimeries biologies aktiewe verbindings daar te stel om
sodoende as ‘n alternatief vir die lae molêre massa biologies aktiewe verbindings, wat tans in
waterverf gebruik word, te dien. ‘n Sekondêre uitkoms van die studie was om te wys dat, sonder
enige adissionele omskakelings, dieselfde polimeer gebruik kan word in seep-vrye emulsie
polimerisasie.
Deur gebruik te maak van ‘n proses, wat uit twee stappe bestaan, het ek ‘n kommersieel beskikbare
kopolimeer, poly(stireen-alt-maleinesuuranhidried) (SMA 1000), met gemengde amiene reageer om
‘n sintetiese lateks van stireen en butiel akrilaat (STY/BuA) met inherente antibakteriële aktiwiteit te
verkry. In die eerste stap is SMA 1000 met 3-dimetielamien-1-propielamien en waterige ammoniak
reageer om ‘n water oplosbare kopolimeer met inherente anti-bakteriële aktiwiteit te verkry. In die
tweede stap is hierdie kopolimeer by ‘n sintetiese lateks gevoeg op twee maniere: (1) deur dit nadat
die lateks geproduseer is by te voeg, en (2) deur die kopolimeer as stabiliseerder te gebruik in die
vervaardiging van die lateks. In albei gevalle is stabiele latekse verkry vir ‘n tydperk van tot 11
maande. Die stabilisering was van steriese geaardheid. Albei die latekse het gevolglik antibakteriële
eienskappe getoon. Daar was nie homogene verspreiding van die aktiwiteit in die geval
waar die kopolimeer na die tyd bygevoeg is nie en het veroorsaak dat daar sekere areas van die
finale film was wat geen aktiwiteit getoon het nie.
Fluoresensie mikroskopie het egter homegene verspreiding van die anti-bakteriële aktiwiteit reg
deur die film getoon, na inokulasie met Gram positiewe bakterië suspensies wanneer die kopolimeer
as polimerisasie stabiliseerder gebruik was. Geen aktiwiteit teen Gram negatiewe bakterië was egter
verkry nie. Die homogene verspreiding was as gevolg van die feit dat die kopolimeer sterk
adsorbeer op elke individuele lateks partikel wanneer dit as stabiliseerder gebruik word. Verdere
ontwikkeling op ‘n kommersiële basis kan daartoe lei dat polimeries biologies aktiewe verbindings
as ‘n lewensvatbare en omgewingsvriendelike alternatief vir heidige stabiliseerders in emulsies vir
waterverf gebruik kan word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17945 |
| Date | 12 1900 |
| Creators | Cloete, William Joseph |
| Contributors | Klumperman, Bert, Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Rights | Stellenbosch University |
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