Self-initiated photografting and photopolymerization (SI-PGP) uses UV illumination to graft polymers to surfaces without additional photoinitiators using the monomers as initiators, “inimers”. A wider use of this method is obstructed by a lack of understanding of the resulting, presumably heterogeneous, polymer structure and of the parallel degradation under continuous UV illumination. We have used neutron reflectometry to investigate the structure of hydrated SI-PGP-prepared poly(HEMA-co-PEG₁₀MA) (poly(2-hydroxyethyl methacrylate-co-(ethylene glycol)₁₀ methacrylate)) films and compared parabolic, sigmoidal, and Gaussian models for the polymer volume fraction distributions. Results from fitting these models to the data suggest that either model can be used to approximate the volume fraction profile to similar accuracy. In addition, a second layer of deuterated poly(methacrylic acid) (poly(dMAA)) was grafted over the existing poly(HEMA-co-PEG₁₀MA) layer, and the resulting double-grafted films were also studied by neutron reflectometry to shed light on the UV-polymerization process and the inevitable UV-induced degradation which competes with the grafting.

Rational design and informed development of nontoxic antifouling coatings requires a thorough understanding of the interactions between surfaces and fouling species. With more complex antifouling materials, such as composites or zwitterionic polymers, there follows also a need for better characterization of the materials as such. To further the understanding of the antifouling properties of charge-balanced polymers, we explore the properties of layered polyelectrolytes and their interactions with charged surfaces. These polymers were prepared via self-initiated photografting and photopolymerization (SIPGP); on top of a uniform bottom layer of anionic poly(methacrylic acid) (PMAA), a cationic poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) thickness gradient was formed. Infrared microscopy and imaging spectroscopic ellipsometry were used to characterize chemical composition and swelling of the combined layer. Direct force measurements by colloidal probe atomic force microscopy were performed to investigate the forces between the polymer gradients and charged probes. The swelling of PMAA and PDMAEMA are very different, with steric and electrostatic forces varying in a nontrivial manner along the gradient. The gradients can be tuned to form a protein-resistant charge-neutral region, and we demonstrate that this region, where both electrostatic and steric forces are small, is highly compressed and the origin of the protein resistance of this region is most likely an effect of strong hydration of charged residues at the surface, rather than swelling or bulk hydration of the polymer. In the highly swollen regions far from charge-neutrality, steric forces dominate the interactions between the probe and the polymer. In these regions, the SIPGP polymer has qualitative similarities with brushes, but we were unable to quantitatively describe the polymer as a brush, supporting previous data suggesting that these polymers are cross-linked.

We report on the preparation and characterization of thin polyampholytic hydrogel gradient films permitting pH-controlled protein resistance via the regulation of surface charges. The hydrogel gradients are composed of cationic poly(2-aminoethyl methacrylate hydrochloride) (PAEMA), and anionic poly(2-carboxyethyl acrylate) (PCEA) layers, which are fabricated by self-initiated photografting and photopolymerization (SIPGP). Using a two-step UV exposure procedure, a polymer thickness gradient of one component is formed on top of a uniform layer of the oppositely charged polymer. The swelling of the gradient films in water and buffers at different pH were characterized by imaging spectroscopic ellipsometry. The surface charge distribution and steric interactions with the hydrogel gradients were recorded by direct force measurement with colloidal-probe atomic force microscopy. We demonstrate that formation of a charged polymer thickness gradient on top of a uniform layer of opposite charge can result in a region of charge-neutrality. This charge-neutral region is highly resistant to non-specific adsorption of proteins, and its location along the gradient can be controlled via the pH of the surrounding buffer. The pH-controlled protein adsorption and desorption was monitored in real-time by imaging surface plasmon resonance, while the corresponding redistribution of surface charge was confirmed by direct force measurements.

ZnO nanostructures of diverse morphology with shapes of corrals and cabbages as well as open and filled hexagons and sheaves prepared by APMOCVD technique, are investigated with water contact angle (CA) analysis. The as-grown ZnO nanostructures exhibit pure hydrophobic behavior, which is enhanced with the increase of the nanostructures surface area. The most hydrophobic structures (CA = 124 degrees) were found to be the complex nanosheaf, containing both the macro-and nanoscale features. It is concluded that the nanoscale roughness contributes significantly to the hydrophobicity increase. The character of wettability was possible to switch from hydrophobic-to-superhydrophilic state upon ultra violet irradiation. Both the rate and amplitude of the contact angle depend on the characteristic size of nanostructure. The observed effect is explained due to the semiconductor properties of zinc oxide enhanced by increased surface chemistry effect in nanostructures.

From macro- to nanoscales, adhesion phenomena are all-pervasive in nature yet remain poorly understood. In recent years, studies of biological adhesion mechanisms, terrestrial and marine, have provided inspiration for "biomimetic" adhesion strategies and important insights for the development of fouling-resistant materials. Although the focus of most contemporary bioadhesion research is on large organisms such as marine mussels, insects and geckos, adhesion events on the micro/nanoscale are critical to our understanding of important underlying mechanisms. Observing and quantifying adhesion at this scale is particularly relevant for the development of biomedical implants and in the prevention of marine biofouling. However, such characterization has so far been restricted by insufficient quantities of material for biochemical analysis and the limitations of contemporary imaging techniques. Here, we introduce a recently developed optical method that allows precise determination of adhesive deposition by microscale organisms in situ and in real time; a capability not before demonstrated. In this extended study we used the cypris larvae of barnacles and a combination of conventional and imaging surface plasmon resonance techniques to observe and quantify adhesive deposition onto a range of model surfaces (CH(3)-, COOH-, NH(3)-, and mPEG-terminated SAMs and a PEGMA/HEMA hydrogel). We then correlated this deposition to passive adsorption of a putatively adhesive protein from barnacles. In this way, we were able to rank surfaces in order of effectiveness for preventing barnacle cyprid exploration and demonstrate the importance of observing the natural process of adhesion, rather than predicting surface effects from a model system. As well as contributing fundamentally to the knowledge on the adhesion and adhesives of barnacle larvae, a potential target for future biomimetic glues, this method also provides a versatile technique for laboratory testing of fouling-resistant chemistries.

Self-assembled monolayers (SAMs) of galactoside-terminated alkanethiols have protein-resistance properties which can be tuned via the degree of methylation [Langmuir 2005, 21, 2971-2980]. Specifically, a partially methylated compound was more resistant to nonspecific protein adsorption than the hydroxylated or fully methylated counterparts. We investigate whether this also holds true for resistance to the attachment and adhesion of a range of marine species, in order to clarify to what extent resistance to protein adsorption correlates with the more complex adhesion of fouling organisms. The partially methylated galactoside-terminated SAM was further compared to a mixed monolayer of omega-substituted methyl- and hydroxyl-terminated alkanethiols with wetting properties and surface ratio of hydroxyl to methyl groups matching that of the galactoside. The settlement (initial attachment) and adhesion strength of four model marine fouling organisms were investigated, representing both micro- and macrofoulers; two bacteria (Cobetia marina and Marinobacter hydrocarbonoclasticus), barnacle cypris larvae (Balanus amphitrite), and algal zoospores (Ulva linza). The minimum in protein adsorption onto the partially methylated galactoside surface was partly reproduced in the marine fouling assays, providing some support for a relationship between protein resistance and adhesion of marine fouling organisms. The mixed alkanethiol SAM, which was matched in wettability to the partially methylated galactoside SAM, consistently showed higher settlement (initial attachment) of test organisms than the galactoside, implying that both wettability and surface chemistry are insufficient to explain differences in fouling resistance. We suggest that differences in the structure of interfacial water may explain the variation in adhesion to these SAMs.

We describe the synthesis of a series of mono-, di-, and trisaccharide-functionalized alkanethiols as well as the formation of fouling-resistant self-assembled monolayers (SAMs) from these. The SAls,,Is were characterized using ellipsometry, wetting measurements, and infrared reflection absorption spectroscopy (WAS). We show that the structure of the carbohydrate moiety affects the packing density and that this also alters the alkane chain organization. Upon increasing the size of the sugar moieties (from mono- to di- and trisaccharides), the structural qualities of the monolayers deteriorated with increasing disorder, and for the trisaccharide, slow reorganization dynamics in response to changes in the environmental polarity were observed. The antifouling properties of these SAMs were investigated through protein adsorption experiments from buffer solutions as well as settlement (attachment) tests using two common marine fouling species, zoospores of the green macroalga Ulva linza and cypris larvae of the barnacle Balanus amphitrite. The SAMs showed overall good resistance to fouling by both the proteins and the tested marine organisms. To improve the packing density of the SAMs with bulky headgroups, we employed mixed SAMs where the saccharide-thiols are diluted with a filler molecule having a small 2-hydroxyethyl headgroup. This method also provides a means by which the steric availability of sugar moieties can be varied, which is of interest for specific interaction studies with surface-bound sugars. The results of the surface dilution study and the low nonspecific adsorption onto the SAMs both indicate the feasibility of this approach.

In this work we have evaluated the haemocompatibility of different surface modifications, intended for biomaterials and biosensor applications. Polystyrene slides were coated with thin hydrogel films by self-initiated photografting of four different monomers. The hydrogel surface modifications were thoroughly characterized and tested for their protein resistance and ability to facilitate platelet adhesion and activation of the coagulation system. There was very little protein adsorption from human plasma on the hydrogels formed from poly(ethylene glycol) methacrylate (PEGMA) and 2-hydroxyethyl methacrylate (HEMA). Platelet adhesion tests performed under both static and flow conditions showed that these coatings also demonstrated very high resistance towards platelet adhesion. A small amount of platelets were found to adhere to hydrogels formed from ethylene glycol methyl ether methacrylate (EGMEMA) and 2-carboxyethyl methacrylate (CEA). The polystyrene substrates themselves facilitated large amounts of platelet adhesion under both static and flow conditions. Utilizing a novel setup for imaging of coagulation, it was shown that none of the hydrogel surfaces activated the coagulation system to any great extent. We suggest that this simple fabrication method can be used to produce hydrogel coatings with unusually high blood compatibility, suitable for demanding biomaterials applications.

Many applications share a substantial and yet unmet need for prediction and control of interactions between surfaces and proteins or living cells. Examples are blood-contacting biomaterials, biosensors, and non-toxic anti-biofouling coatings for ship hulls. The main focus of this thesis work has been the synthesis, characterization and properties of a group of coatings, designed for such applications. Many types of substrates, particularly plastics, were coated directly with ultrathin, hydrophilic polymer coatings, using a newly developed polymerization method initiated by short-wavelength ultraviolet light.

The thesis contains eight papers and an introduction aimed to provide a context for the research work. The common theme, discussed and analyzed throughout the work, has been the minimization of non-specific binding of proteins to surfaces, thereby limiting the risk of uncontrolled attachment of cells and higher organisms. This has mainly been accomplished through the incorporation of monomer units bearing poly(ethylene glycol) (PEG) side chains in the coatings. Such PEG-containing “protein resistant” coatings have been used in this work as matrices for biosensor applications, as blood-contacting inert surfaces and as antibiofouling coatings for marine applications, with excellent results. The properties of the coatings, and their interactions with proteins and cells, have been thoroughly characterized using an array of techniques such as infrared spectroscopy, ellipsometry, atomic force microscopy, surface plasmon resonance and neutron reflectometry. In addition, other routes to fabricate coatings with high protein resistance have also been utilized. For instance, the versatility of the fabrication method has enabled the design of gradients with varying electrostatic charge, affecting the protein adsorption and leading to protein resistance in areas where the charges are balanced.

This thesis also describes a novel application of imaging surface plasmon resonance for the investigation of the surface exploration behavior of marine biofouling organisms, in particular barnacle larvae. This technique allows for real-time assessment of the rate of surface exploration and the deposition of protein-based adhesives onto surfaces, a process which was previously very difficult to investigate experimentally. In this thesis, the method was applied to several model surface chemistries, including the hydrogels described above. The new method promises to provide insights into the interactions between biofouling organisms and a surface during the critical stages prior to permanent settlement, hopefully facilitating the development of antibiofouling coatings for marine applications.