Films engineered to control the transport of liquids are widely used through society. Examples include barriers in packaging, wound care products, and controlled release coatings in pharmaceutics. When observed at the macroscopic scale such films commonly appear homogeneous, however, a closer look reveals a complex nano- and microstructure that together with the chemical properties of the different domains control the transport properties. In this review we compare and discuss macroscopic transport properties, measured using the straightforward, yet highly powerful technique "modified Ussing chambers", also denoted side-by-side diffusion cells, for a wide range of structured polymer films and composites. We also discuss and compare the macroscopic observations and conclusions on materials properties with that of lattice Boltzmann simulations of transport properties based on underlying material structure and chemistry. The survey of the field: (i) highlights the use and power of modified Ussing Chambers for determining liquid transport properties of polymer films, (ii) demonstrates the predictability in both directions between macroscopic observations of transport using modified Ussing chambers and structure-based simulations, and (iii) provides experimental and theoretical insights regarding the transport-determining properties of structured polymer films and composites.

Composite films were sprayed from mixtures of water soluble hydroxypropyl methylcellulose (HPMC) and either nanofibrillated cellulose (NFC) or cellulose nanocrystals (CNC). Fiber diameter was similar for both nanocelluloses but fiber length was several μm for NFC and about 200nm for CNC. Films were characterized for morphology, swelling, mass loss and transport properties. NFC-HPMC films swelled less than CNC-HPMC films; with a HPMC content of 20wt% NFC-HPMC and CNC-HPMC films presented swelling of 7 and 75g/g, respectively. The swelling strongly influenced water transport across the films, with slower transport for CNC-based materials compared to NFC-based materials. The properties of NFC-based films were comparable to previous results using microfibrillated cellulose (MFC) with heterogeneous structural content and fiber lengths of ~10μm. The findings have implications for using nanocellulose to modulate material properties in wet-state applications, with effects being in strong contrast when using as a hardening filler in dry materials.

This paper deals with a novel method for improving the traditional “verification” laboratory in science education. Drawing on the idea of integrated instructional units, we describe an instructional sequence which we call the Babushka concept. This concept consists of three integrated instructional units: a start-up lecture, a laboratory session and a wrap-up lecture. Like the Russian nested doll, the sequence has a nested conceptual structure, moving from “bigger” questions to “smaller” ones. The students are actively involved during the lectures by answering reflective questions. This careful sequencing of ideas and activities aims to help the students to relate new ideas to prior knowledge, and to understand the purpose of the laboratory activity. The Babushka concept was implemented in a master’s course in pharmaceutical technology and its impact was evaluated using both qualitative and quantitative methods. The evaluation focused on the students’ perceptions of the intervention as well as their learning gains. A majority of the students found the Babushka concept helpful for their learning and agreed that this concept should be used in other courses. Moreover, the number of correct answers on the final written exam increased by 10%. We briefly discuss one way to enhance the Babushka concept.

We suggest a rough and straightforward method to predict the dispersibility of modified cellulose nanocrystals (CNC) in nanocomposites using Hansen solubility parameters (HSP). The surface of CNC was modified using a novel approach where Y-shaped substituents with two different carbon chain lengths were attached to the surface. Approximate HSP values were calculated for the modified CNC, and dispersions of unmodified and modified CNC in solvents with varying HSPs were studied. The best dispersibility was observed in dichloromethane, when the CNC surface was modified with longer carbon chains. Dichloromethane has HSP similar to low-density polyethylene (LDPE). Nanocomposites with both unmodified and modified CNC were produced. The materials with modified CNC showed increased adhesion between the filler and the matrix, followed by a decreased water permeability compared to unmodified CNC, suggesting a better dispersibility of modified CNC in LDPE and confirming the usefulness of this approach.

Cellulose esters with long carbon side chains (e.g. stearate) were produced via a homogenous reaction in ionic liquids. The degree of substitution was calculated to approximately 2. The melt rheology was studied for the pure cellulose esters but also combinations of the esters and polypropylene to study the processability of a blended composite material. It was shown that the compatibility between the two components was weak, which resulted in a phase-separated composite material. The morphology and permeability of water and oleic acid of the composite films were studied and it was shown that the water permeability decreased upon addition of the cellulose ester to the polymer. The permeability of oleic acid was however unchanged, which is most probable a result of high solubility in the cellulose ester rich domains of the composites. Also, the following hypothesis is stated: cellulose stearate influence the polypropylene crystallization process by decreasing the size of spherulites.

Previous investigations of aqueous based ethyl cellulose (EC) latex dispersions have mainly focused on the commercially available viscosity grade 20cps. In this study, dispersions of EC with varying viscosity grades (which correspond to molecular weights), ranging from 4 to 100 cps, were produced and characterised. The dispersions showed particle sizes around 200nm and highly negative ζ-potentials (approx. -100mV), which indicated stable dispersions as confirmed by sedimentation studies. The different latexes were used to produce free-standing film coatings. We hypothesised that the different viscosity grades of EC would result in different properties of the films. We found that an increase in viscosity grade (and higher molecular weight) resulted in lower coalescence between the particles during film formation and thus to higher water permeability than in film coatings of lower molecular weight. After exposure to water the EC 4cps and 20cps film coatings had a more porous structure in the side facing the air during production and drying after immersion in water. Molecular weight is therefore a factor that should be considered when producing pharmaceutical coatings for controlled release.

The permeability of oleic and acetic acid through low density polyethylene (LDPE) and ethylene acrylic acid (EAA) have been measured using diffusion cells. In addition, the permeability through combinations of LDPE and EAA in the form of laminates with different numbers of layers has been determined. Oleic acid shows an almost 30 times higher permeability compared to acetic acid, which was partly explained by the adsorption of oleic acid to the film surface during the permeability experiment. In addition, the permeability is lower for both oleic and acetic acid in the laminates compared to the pure films. The decreased permeability can be explained by the presence of crystalline domains close to the interface. This is supported by SAXS data which suggests an ordering of polymer chains in the EAA film close to the interface. In summary, the results show that it is possible to create barrier materials with decreased permeability, which is interesting for example in the packaging industry.

ABSTRACTTo test the hypothesis that the introduction of a hydrophilic hemicellulose would affect viscoelastic properties and increase water permeability, xyloglucan (XG) was adsorbed onto the surface of microcrystalline cellulose (MCC) in water dispersion prior to the extrusion of 79–80 wt % polylactide acid (PLA), 20 wt % MCC, and 0–1 wt % XG. For comparison, composites of PLA, MCC, and non‐absorbed XG were produced. Analysis of thermal properties showed no differences for glass‐transition or melting temperatures, but the crystallinity of the films increased with the addition of MCC and XG. Storage modulus of the composite materials increased with XG content; however, at higher humidities storage modulus decreased, probably because of lower interfacial adhesion. Water permeability through the films increased more with the addition of XG adsorbed to the MCC than with the MCC and XG simply mixed in the same amounts. © 2014 The Authors. Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41219.

Nano-rod reinforced materials for example with cellulose nanocrystals (CNC) has shown great potential. It is common to optimize the compatibility between cellulose, polymer and solvent in order to improve material properties. Here we show that increased compatibility will give more porous films, which from many points of view can be a drawback, e.g. an increased porosity in the material can decrease mechanical and barrier properties. It was hypothesized that the addition of higher amounts of a rod-like nano-filler, i.e. up to 20 wt% to a composite material will cause the nano-rods to overlap, lock the system and introduce pores and cavities to the final material. In order to investigate the hypothesis, nano-composite films consisting of the matrix materials polylactide acid (PLA) or poly(lactide-co-glycolide) (PLGA) and the nano-filler cellulose nanocrystals were produced via solvent casting and the morphology, density and water permeability were studied for the produced films. The addition of both unmodified and modified CNC to the matrix polymers resulted in materials where pores and cavities were present, which was more evident for the modified CNC that was more homogeneous dispersed into the matrix. The presence of pores in the films resulted in decreased density and increased water permeability. The solvent casted films were hot-melt pressed to reduce the amounts of pores and cavities but density and water permeability measurements for the pressed films showed that it was difficult to remove all cavities using melting and pressing procedure. (C) 2014 Elsevier Ltd. All rights reserved.

The surface of cellulose nanocrystals (CNC) was chemically modified with polylactic acid. The modification was characterized by infrared spectroscopy, by monitoring the colloidal behavior of CNC in different solvents, and by quantitative analysis using solid-state NMR (ss-NMR). The quantitative analysis showed that grafted PLA chains on average comprised two lactic acid units attached to 48% of all available hydroxyl groups on the surface of the CNC. Both modified and unmodified CNC were incorporated as fillers in three different biodegradable materials: polylactide acid (PLA), poly(lactide-co-glycolide) (PLGA) and poly(3-hydroxybutyrate) (PHB). Composite films with up to 20wt% of unmodified and modified CNC were produced via solvent casting. Compared to unmodified CNC, the modified CNC showed less aggregation in organic solvents and hydrophobic polymer materials and increased interaction was seen between the polymer and filler after surface modification. Using ss-NMR, our study shows that even as little as two units of PLA assures stabile CNC dispersions in organic solvents and distribute CNC in hydrophobic polymers.

SUMMARY In this study, biodegradable films consisting of polylactic acid (PLA) and nano-crystalline cellulose (NCC) have been produced in order to study their use as future implant materials. The two materials have been shown to have poor adhesion. To increase the compatibility, the surface of NCC was modified with PLA-chains. The thermal and mechanical properties as well as the water permeability were investigated and compared for different ratios of filler material. INTRODUCTION Polylactic acid (PLA) is a biodegradable polymer with low toxicity and high mechanical strength (1). These properties make the polymer suitable for products ranging from packaging materials to biomedical devices such as sutures, implants and drug delivery systems. The use of biodegradable implants has also been considered to be an alternative to metal implants. The advantage is mainly that the implant does not need to be removed, resulting in less trauma and pain for the patient. Even though PLA has mechanical strength, it may sometimes not be enough for example if a bone is highly loaded. The mechanical strength can then be improved by the addition of nano-particles. In this study we have reinforced the material by the use of nano-crystalline cellulose (NCC). NCC is also a degradable polymer, which results in a totally degradable implant. However, the adhesion between PLA and cellulose has been shown to be poor, resulting in an inflexible and brittle material. Therefore, we attached PLA chains onto the surface of the NCC particles via a ring opening polymerization (Figure 1). Composite films with varying amount of NCC were thereafter produced via solvent casting. An important factor to consider for biodegradable implants is the degradation. PLA is degraded via hydrolysis of the ester bond and therefore the water transport within the material is of interest. Also, mechanical and thermal properties as well as the morphology of the materials were studied. EXPERIMENTAL METHODS NCC was produced as earlier described in literature (2). The modification was performed by a ring opening polymerization of L-lactide in presence of NCC (Figure 1). Briefly, the water in the NCC suspension was exchanged into DMSO, and Llactide, tin(II)ethylhexanoate and benzyl alcohol was added and the reaction was performed at 130°C for 17 hours while stirred. The final product was washed with water and acetone in several steps. Figure 1: Reaction scheme for the surface modification of nanocrystalline cellulose via ring opening polymerization of L-lactide. Modification was confirmed by Infrared spectroscopy (IR), ss-NMR and the behavior of the particles in different solvents. Composite films with 1, 5 and 10 wt% of NCC were produced via solvent casting. The solvent was exchanged into dichloromethane (DCM) prior casting and PLA was added and left to dissolve. The solution was poured into a petridish and the solvent was allowed to evaporate overnight. Pure PLA films were produced in the same manner. The films were kept in a desiccator until use. The mechanical and thermal properties were studied using an Instron 5565A device, and a Perkin Elmer Pyris 1 Differential Scanning Calorimetry respectively. The morphology was studied in a Scanning Electron Microscope (Leo Ultra FEGSEM). Water permeability was measured in diffusion cells were the film was placed between a donor and an acceptor chamber. Tritium labeled water was added to the donor chamber and the accumulation of the water was sampled over time. The radioactivity was measured in a Perkin Elmer Liquid Scintillation Analyzer. The permeability of the material was calculated from the linear region of a plot of the accumulated water against time. RESULTS AND DISCUSSION The surface modification of NCC was determined from the appearance of a carbonyl peak in the IR-spectra and the ss-NMR spectra (not shown here). The dispersibility (Figure 2) of the modified (right) and unmodified (left) NCC is shown in different solvents. NCC is known to have a good dispersibility in water due to the surface charges (Figure 2a). The modified NCC showed a tendency to flocculate and sediment over time, probably due to hydrophobic interactions. However, when NCC was placed in organic solvents the modified NCC was well dispersed while unmodified NCC formed aggregates (Figure 2b-c). Figure 2: Photographs showing the dispersibility of 0.7% (w/w) of modified NCC (left) and NCC (right) in different solvents. (a) Water (b) Isopropyl alcohol (c) Dichloromethane. The mechanical properties showed an increase in Young ́s modulus for the unmodified NCC films up to 55% compared to the pure PLA film. At the same time, the elongation of the composite films decreased with 50%. However, for the unmodified NCC the value of moduli and elongation was quite constant. The crystallinity for the pure PLA and composite film with unmodified NCC was less than 2%. The crystallinity increased to 4% and 7% when 5 respectively 10 wt% of modified NCC was added, showing that the modified NCC may function as a nucleating agent in the films. The morphology of the cross-sections of the films was studied with SEM and the pure PLA film (Figure 3a) showed a smooth surface. The composite films had a rougher surface, however the modified NCC seems to be better incorporated to the matrix material (Figure 3b) than the unmodified NCC (Figure 3c). Figure 3: SEM images showing the cross-section of (a) pure PLA, (b) PLA with 5 wt% modified NCC, (c) PLA with 5 wt% unmodified NCC. The water permeability is presented in Figure 4 and the addition of the unmodified NCC did not show a significant different for the permeability. However, the addition of modified NCC resulted in increased water permeability. This was not an expected result though the crystallinity is higher in the unmodified NCC films; the permeability was believed to decrease. A possible explanation is that the water permeability increases due to that there are some voids or channels formed along the interface between the particles and the matrix material, which may function as a path for water to be transported through the material. Figure 4: Water permeability of composites of PLA and unmodified NCC (◊) and modified NCC (●). The error bars represent the standard deviation of each value. CONCLUSION The addition of NCC to a PLA film resulted in an increased or constant Young ́s modulus, which may be desired in an implant. The crystallinity was not affected by the addition of unmodified NCC while the modified NCC increased the crystallinity six times. However, the water transport through the composite films was increased when the modified NCC was added. This may be an important factor to consider if the composite material is to be used in an implant, since PLA is degraded by hydrolysis and an increased water transport may result in a faster degradation. REFERENCES 1. Södergård A, Stolt M. Progress in Polymer Science. 2002, 27, 1123-63. 2. Bondeson, B.; Mathew, A.; Oksman K. Cellulose. 2006, 13, 171-180. 3. Raj, G., Balnois, E. et al. J. Mater. Sci. 2012, 47, 2175-2181. ACKNOWLEDGMENTS The project is part of the VINN Excellence SuMo Biomaterials (Supermolecular Biomaterials – Structure dynamics and properties). The financial support from the Centre is gratefully acknowledged.

Synthesis of bis-4,5-diazafluoren-9-one silver(I) nitrate I (dafone = 4,5-diazafluoren-9-one) and the low temperature X-ray single crystal structure of [Ag(4,5-diazafluoren-9-one)2NO3], crystal form 1, and a re-determination of [Ag(4,5-diazafluoren-9-one)2]NO3·H2O, crystal form 2 are presented. Crystal form 1 has a distorted trigonal planar coordination geometry around Ag(I) with an N–Ag–N bond angle of 123.45(7)°. Crystal form 2 has a perfect linear coordination around Ag, with N–Ag–N 180.0°. Compound I was characterized by 1H-NMR, biological activity and ESI-MS in DMSO at room temperature. The biological activity was determined against 6 different resistant clinical isolates; two Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and four Gram-negative (Pseudomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, and Salmonella sp.) in comparison with 15 known antibiotics used in the treatment of diabetic foot infections. Compound I showed broad spectrum activity against all the test organisms. P. mirabilis and S. aureus and K. pneumoniae were the most sensitive clinical isolates (MIC = 4, 6 and 4 μg ml−1, respectively). Three different hydrogels containing I or Ag2SO4 were prepared and the antimicrobial activity against Ps. aeruginosa (ATCC 15442) compared, showing more or less equal activity on a weight basis, but I seems to have a significant better performance per silver ion. The Ag(I) complex also binds more effectively to calf thymus DNA than the dafone ligand itself.