Jaan Erik Roots

• Truong, Thuy le; Larsen, Åge Gellein & Roots, Jaan (2017). Morphology, crystalline features, and tensile properties of syndiotactic polypropylene blends. Journal of Applied Polymer Science. ISSN 0021-8995. 134(12). doi: 10.1002/app.44611. Full text in Research Archive Show summary

  Syndiotactic polypropylene (sPP) was modified with ethylene–octene copolymer (EOC) and ethylene–propylene rubber (EPR), with test samples prepared in a twin-screw extruder and then injection-molded. The phase morphology, rheology, and thermal and tensile properties of the modified sPP were investigated. Atomic force microscopy studies showed how the phase morphology of the sPP blends with elastomers depended on the blend compositions, and the results compared with the storage modulus at low frequency. EOC and EPR were dispersed phase in an sPP matrix with spherical shapes when the dispersed content was 20 wt % or lower. The phase cocontinuity started around 40 wt % EOC for the sPP–EOC blends and around 60 wt % EPR for the sPP–EPR. The dispersed phase then formed more complex elongated shapes. The rheological and thermal properties were affected by the sPP–elastomer interphase. EOC promoted the crystallization of sPP; this increased the crystallization temperature and rate. In contrast, EPR had the opposite effect on the crystallization behavior, and the results indicate that sPP and EPR were not completely separated. The tensile properties were studied from −20 to 100 °C. We found that the tensile properties at low temperature could be improved without a loss in high-temperature properties. In the particular case of 20 wt % EOC, both the strain at yield and strain at break of the sPP–EOC blend were improved at both −20 and 100 °C.

• Paul, Jobby; Hansen, Eddy Walther & Roots, Jaan (2013). Application of single-pulse solid-state H-1-MAS NMR to probe the oxidation products in crosslinked polyethylene: A detailed spectral analysis procedure. Polymer degradation and stability. ISSN 0141-3910. 98(1), p. 408–415. doi: 10.1016/j.polymdegradstab.2012.08.025.
• Truong, Thuy le; Larsen, Åge Gellein; Holme, Børge & Roots, Jaan (2012). Nonisothermal melt crystallization kinetics of syndiotactic polypropylene/alumina nanocomposites. Journal of Applied Polymer Science. ISSN 0021-8995. 126(4), p. 1198–1206. doi: 10.1002/app.36875. Show summary

  Nonisothermal melt crystallization kinetics of syndiotactic polypropylene (sPP)/alumina nanocomposites were investigated via differential scanning calorimetry. The addition of alumina nanoparticles significantly increases the number of nuclei and promotes the crystallization rate of sPP. Nonisothermal melt crystallization kinetics was analyzed by fitting the experimental data to a Nakamura model using Matlab. The average values of Avrami exponent n are 1.7 for both sPP and sPP/Al2O3 nanocomposites during slow cooling, which implies a two-dimensional growth is the predominant mechanism of crystallization following a heterogeneous nucleation. The two nanocomposites give n values equal to 2.3 during faster cooling, indicating that the main growth type taking place for sPP/alumina nanocomposites is also the two-dimensional growth. The subsequent melting behavior shows that the presence of alumina nanoparticles changed both the cold crystallization and the recrystallization of sPP. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

• Paul, Jobby; Hansen, Eddy Walther & Roots, Jaan (2012). Probing the molecular dynamics in XLPE aged at different temperatures by H-1 NMR relaxation time measurements. Polymer degradation and stability. ISSN 0141-3910. 97(11), p. 2403–2411. doi: 10.1016/j.polymdegradstab.2012.07.022.
• Poltimae, Triinu; Tarasova, Elvira; Krumme, Andres; Roots, Jaan & Viikna, Anti (2011). Thermal Analyses of Blends of Hyperbranched Linear Low-density Polyethylene (LLDPE) with High-density Polyethylene and LLDPE Prepared by Dissolving Method. Materials Science. ISSN 1392-1320. 17(3), p. 254–259. doi: 10.5755/j01.ms.17.3.589.
• Haddad, Raoudha; Holzinger, Michael; Villalonga, Reynaldo; Neumann, Astrid Brigitte; Roots, Jaan & Maaref, A. [Show all 7 contributors for this article] (2011). Pyrene-adamantane-beta-cyclodextrin: An efficient host-guest system for the biofunctionalization of SWCNT electrodes. Carbon. ISSN 0008-6223. 49(7), p. 2571–2578. doi: 10.1016/j.carbon.2011.02.049.
• Truong, Thuy le; Larsen, Åge Gellein; Holme, Børge; Hansen, Finn Knut & Roots, Jaan (2011). Morphology of syndiotactic polypropylene/alumina nanocomposites. Polymer. ISSN 0032-3861. 52(4), p. 1116–1123. doi: 10.1016/j.polymer.2011.01.014. Show summary

  The effect of the addition of 50 nm spherical alumina nanoparticles with hydrophilic or hydrophobic surfaces on the morphology of syndiotactic polypropylene (sPP) was investigated. The filler content in the nanocomposites was 3 wt%. Polarized Optical Microscopy and Small Angle Light Scattering (SALS) studies showed that sPP and the nanocomposites form hedrites. The addition of alumina nanoparticles significantly increased the number of hedrites. A higher number of nucleation sites in the nanocomposites promote a higher crystallization rate, and thus hedritic growth was stopped at the early stage of crystallization. Quantitative evaluations by SALS analysis show that the object size is decreased by not only the crystallization conditions but also the presence of Al2O3 nanoparticles. A small amount of Al2O3 nanoparticles did not noticeably affect the crystallinity of sPP, but increased the melting point. Transmission Electron Microscopy images showed that the lamellar thickness did not change significantly with the incorporation of nanoparticles. The lamella thickness, however, depends on cooling rates. X-ray diffraction characterization indicated that the sPP and the nanocomposites were crystallized in disordered “form I”. The incorporation of alumina nanoparticles had a small effect on the crystal structure of syndiotactic polypropylene.

• Bjørnsen, Geir & Roots, Jaan (2011). Plasma etching of polydimethylsiloxane: Effects from process gas composition and dc self-bias voltage. Journal of Vacuum Science & Technology B. ISSN 1071-1023. 29(1). doi: 10.1116/1.3521489. Show summary

  Films made of polydimethylsiloxane elastomers have been etched using reactive ion etching. The elastomers are etched using different mixtures of CF4, SF6, and O2 as process gases. The etch rate and profile of the etched area are measured as function of the process pressure for different process gas compositions. At low pressure the highest etch rate is achieved in SF6+O2 plasma. At high pressure the highest etch rate is achieved in CF4+SF6+O2 plasma. The profile of the etched surface is strongly dependent on the process gas composition and the dc bias voltage in the plasma.

• Bjørnsen, Geir; Roots, Jaan & Henriksen, Lars (2011). Patterning of soft polydimethylsiloxane elastomers using plasma etching. Journal of Applied Polymer Science. ISSN 0021-8995. 119(2), p. 888–895. doi: 10.1002/app.32760. Show summary

  Soft polydimethylsiloxane (PDMS) elastomers spin coated on silicon wafers are patterned using plasma etching. The elastomers are formed by mixing vinyl-terminated PDMS (prepolymer) and crosslinker containing hydride sites. The elastomers are made softer by adding either excess prepolymer, excess crosslinker, or swelling agent. The different elastomers were etched using reactive ion etching, an old and well established processing technology in the microelectronic and MEMS industry. The etch rate and profiles of the etched surfaces were dependent on the process pressure. The dependence was different for the different elastomers. It was found that at low pressure, the etch rate was dependent on the shear modulus. At high pressures, the etch rate was dependent on the chemical composition of the elastomer. The results for the swollen elastomers were different from those for the nonswollen elastomers. The etch rate was lower and the profiles of the etched cavities were different.

• Truong, Thuy le; Larsen, Åge; Holme, Børge; Diplas, Spyridon; Hansen, Finn Knut & Roots, Jaan (2010). Dispersibility of silane-functionalized alumina nanoparticles in syndiotactic polypropylene. Surface and Interface Analysis. ISSN 0142-2421. 42(6-7), p. 1046–1049. doi: 10.1002/sia.3166.
• Bjørnsen, Geir; Henriksen, Lars; Ulvensøen, Jon Herman & Roots, Jaan (2010). Plasma etching of different polydimethylsiloxane elastomers, effects from process parameters and elastomer composition. Microelectronic Engineering. ISSN 0167-9317. 87(1), p. 67–71. doi: 10.1016/j.mee.2009.05.024. Show summary

  Plasma etching of three different polydimethylsiloxane elastomers has been studied. One elastomer was a commercially available kit (Sylgard-184) and the other two were made by mixing individual components. The etching was done in a multi-wafer tool. The process gas used in the etching was a mixture of SF6 and O2. The etch rate was measured as a function of pressure for all three materials at the centre and the edge of the etched structures. It was found that fillers in the elastomer reduces the etch rate but has little effect on the shape of the etched surface. Second, it was found that excess of chain ends in the elastomer gives larger changes in the shape of the etched surface, as pressure changes. Third, it was found that loading (reduction of etch rate) is significant in the presence of dummy silicon wafers compared to glass wafers. Keywords: PDMS elastomer; Plasma etch; Reactive ion etch (RIE)

• Hansen, Eddy Walther & Roots, Jaan (2010). DETERMINATION OF CRYSTALLINITY IN POLYETHYLENE FROM 1H-NMR FID ANALYSIS EFFECT OF NON-CURIE TEMPERATURE BEHAVIOUR. International Journal of Research Reviews in Applied Sciences. ISSN 2076-734X. 5(3), p. 207–212. Show summary

  Hansen and coworkers (Zhang, L; Hansen, E. W.; Helland, I; Hinrichsen, E.; Larsen, Aa.; Roots, J. Macromolecules, 2009, 42 (14), 5189-5195) recently reported on the room temperature crystallinity of a series of ethene-1-hexene copolymers using solid-state 1H-NMR FID analysis. However, due to the required 10 s blanking time of the receiver vital information in the initial part of the FID was lost resulting in an underestimation of the sample crystallinity. To compensate for this information loss we made use of the significant increase in T2 at or above the melting point which enabled the intensity of the FID at time t = 0 to be reliably estimated. Hence, by applying the Curie law the room temperature intensity of the FID was re-evaluated and resulted in an improved crystallinity value. However, it was still too small compared to the crystallinity obtained by solid-state 13C-NMR. However, by multiplying the proton FID intensity (determined at the melting point) by a factor of 1.25 before applying the Curie law, the room temperature crystallinity derived from the two different NMR techniques became – within experimental error – consistent. In this work we present experimental evidence that the empirical multiplication factor of 1.25 strictly originates from a non-Curie temperature behaviour of the NMR signal intensity.

• Zhang, Lili; Hansen, Eddy Walther; Helland, Irene; Hinrichsen, Einar; Larsen, Åge & Roots, Jaan (2009). Crystallinity in Ethene-1-Hexene Copolymers Determined by H-1 and C-13 NMR. A Comparative Study. Macromolecules. ISSN 0024-9297. 42(14), p. 5189–5195. doi: 10.1021/ma900249z.
• Krumme, Andres; Lehtinen, Arja; Adamovsky, Sergey; Schick, Christoph; Roots, Jaan & Viikna, Anti (2008). Crystallization behavior of some unimodal and bimodal linear low-density polyethylenes at moderate and high supercooling. Journal of Polymer Science Part B: Polymer Physics. ISSN 0887-6266. 46, p. 1577–1588. doi: 10.1002/polb.21494.
• Hansen, Eddy Walther; Norby, Poul; Roots, Jaan & Wu, Qinglan (2007). Gelation of Delaminated Layered Double Hydroxide Nanosheets in Formamide Probed by Proton Spin-Spin Relaxation and Pulsed Field Gradient NMR. Journal of Physical Chemistry C. ISSN 1932-7447. 111(32), p. 11854–11861. doi: 10.1021/jp072273n. Show summary

  A colloid dispersion of exfoliated nanosheets of a layered double hydroxide (LDH-NO3) was prepared by ultrasonic treatment for 4-5 h in formamide. A slow gelation process takes place, which was followed using proton spin-spin relaxation and pulsed field gradient (PFG) NMR. On the NMR time scale, the LDH particles were considered as a nonmobile matrix surrounded by mobile formamide molecules, thus resembling a porous medium. The spatial constraints (micrometer range) imposed on the formamide molecules increase monotonically with time when the LDH particles rearrange and form a "network" during the gelation process, resulting in a faster diffusion of formamide within this "porous" medium. By combining proton NMR spin-spin relaxation rate measurements (1/T2) and PFG-NMR measurements (diffusion), the size of the spatial restrictions formed by the LDH particles was probed as a function of time. The physical model applied in the analysis is discussed in the text.

• Wu, Qinglan; Sjastad, AO; Vistad, OB; Knudsen, KD; Roots, Jaan & Pedersen, JS [Show all 7 contributors for this article] (2007). Characterization of exfoliated layered double hydroxide (LDH, Mg/Al=3) nanosheets at high concentrations in formamide. Journal of Materials Chemistry. ISSN 0959-9428. 17. doi: 10.1039/b612389a.
• Wu, Qinglan; Olafsen, Anja; Vistad, Ørnulv; Roots, Jaan & Norby, Poul (2005). Delamination and restacking of a layered double hydroxide with nitrate as counter anion. Journal of Materials Chemistry. ISSN 0959-9428. 15(44), p. 4695–4700. doi: 10.1039/b511184f.
• Nordby, Marianne Hiorth; Kjøniksen, Anna-Lena; Nyström, Bo & Roots, Jaan (2003). Thermoreversible Gelation of Aqueous Mixtures of Pectin and Chitosan. Rheology. Biomacromolecules. ISSN 1525-7797. 4(2), p. 337–343.
• Baldursdottir, Stefania; Kjøniksen, Anna-Lena; Karlsen, Jan; Nyström, Bo; Tønnesen, Hanne Hjorth & Roots, Jaan (2003). Riboflavin-Photosensitized Changes in Aqueous Solutions of Alginate. Rheological Studies. Biomacromolecules. ISSN 1525-7797. 4(2), p. 429–436.
• Kjøniksen, Anna-Lena; Nordby, Marianne Hiorth; Roots, Jaan & Nyström, Bo (2003). Shear-Induced Association and Gelation of Aqueous Solutions of Pectin. Journal of Physical Chemistry B. ISSN 1520-6106. 107(26), p. 6324–6328.
• Baldursdottir, Stefania; Kjøniksen, Anna-Lena; Roots, Jaan; Tønnesen, Hanne Hjorth & Nyström, Bo (2003). Influence of Concentration and Molecular Weight on the Photosensitized Degradation in Aqueous Alginate Solutions. Polymer Bulletin. ISSN 0170-0839. 50(5-6), p. 373–380.
• Tho, Ingunn; Kjøniksen, Anna-Lena; Nyström, Bo & Roots, Jaan (2003). Characterization of Associations and Gelation of Pectin in Methanol-Water Mixtures. Biomacromolecules. ISSN 1525-7797. 4(6), p. 1623–1629.
• Marstokk, Olav & Roots, Jaan Erik (1999). Synthesis and characterization of hydrophobically modified poly(vinyl alcohol). Polymer Bulletin. ISSN 0170-0839. 42, p. 527–533. Show summary

  Two different routes for the preparation of hydrophobically modified poly(vinyl alcohol), PVA are reported. The first method involves the formation of the polymeric alcoholate. An alkylhalide and propanesulfonate are coupled with the polymer in two subsequent steps of the Williamson ether synthesis. The product is a hydrophobically modified polymer with anionic functionality. The other method proceeds via a 1,4 addition of acrylamide and the Hoffman degradation of the amide to an amine. In the next step, the amine is alkylated with an alkylhalide. The polymers are characterised by quantitative H NMR spectroscopy and titration.

• Roots, Jaan Erik; Ma, Kuangbiao; Higgins, J.S. & Arrighi, V. (1999). Quasilelastic neutron scattering study of poly(dimethyl siloxane) at high pressure. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 1, p. 137–141.
• Marstokk, Olav; Nyström, Bo & Roots, Jaan (1998). Effect of denaturant and polymer concentration on the structural and dynamic properties of aqueous solutions of poly(N-acetamido acrylamide). Macromolecules. ISSN 0024-9297. 31, p. 4205–4212.

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• Paul, Jobby; Hansen, Eddy Walther; Roots, Jaan & Jørgensen, Sissel (2012). Thermal Oxidation of XLPE monitored by solid state 1H-NMR.
• Hansen, Eddy Walther; Paul, Jobby; Roots, Jaan; Jørgensen, Sissel; Poltimae, T & Krumme, Andres (2012). Easy access to the amount of short chains in ethene/alfa-alkene copolymers from solid state 1H-MAS NMR. Show summary

  Abstract Solid state 1H-MAS NMR is shown to be an attractive experimental technique for determining the comonomer content in ethene-alfa-alkene copolymers. Its advantage is associated with: a) no particular need for sample preparation, b) non-destructive, c) short overall acquisition time of the order of a few minutes. d) no need for calibration and finally e) the copolymer content in cross-linked LDPE may be determined, which is otherwise not easily accessible, as these samples are non-soluble in most liquids. References E. W. Hansen, J. Paul, S. Jørgensen, B. Arstad and A. Bouzga, IJRRAS, 2011, 6, 382–390.

• Truong, Le Thuy; Larsen, Åge Gellein; Holme, Børge; Diplas, Spyros; Hansen, Finn Knut & Roots, Jaan (2009). Dispersibility of Silane-functionalized Alumina Nanoparticles in Syndiotactic Polypropylene.
• Truong, Le Thuy; Larsen, Åge; Holme, Børge; Hansen, Finn Knut & Roots, Jaan (2009). Morphology and crystallization behavior of syndiotactic polypropylene-alumina nanocomposites.
• Bjørnsen, Geir; Ulvensøen, Jon Herman; Henriksen, Lars & Roots, Jaan (2008). Patterning of soft polydimethylsiloxane for optical applications.
• Neumann, Astrid; Glerup, Marianne; Roots, Jaan & Holzinger, Michael (2008). Anionic polymerization on SWCNTs.
• Nyström, Bo; Roots, Jaan; Karlsen, Jan & Tønnesen, Hanne Hjorth (2002). Hydrogeler: Skreddersydde materialer. Apollon : Forskningsmagasin for Universitetet i Oslo. ISSN 0803-6926. 4(12), p. 32–34.
• Nordby, Marianne Hiorth; Sande, Sverre Arne; Roots, Jaan Erik & Nyström, Bo (2002). Thermoreversible gelation in acidic aqueous mixtures of chitosan and pectin.
• Baldursdottir, Stefania; Nyström, Bo; Kjøniksen, Anna-Lena; Roots, Jaan; Karlsen, Jan & Tønnesen, Hanne Hjorth (2002). Degradation of Alginate by Riboflavin Photosensitizer. Show summary

  Purpose: The possibility of using photosensitized degradation of biopolmers in order to develop a light activated drug delivery system was investigated. Riboflavin was added to solutions of alginate and the viscosity of the samples was measured as a function of irradiation time. Various quenchers and scavengers were added to the system in order to obtain information on the degradation process. Methods: The alginate samples were exposed to a xenon lamp (1.8kW) equipped with a glass filter transmitting light corresponding to exposure behind window glass (cut-off ~310nm). Changes in sample viscosity was determined by use of a Bohlin rheometer. Chemical- and/or conformational changes in the alginate structure were characterized by light scattering methods. The absorbance and fluorescence spectra of the samples were recorded to detect possible interactions between the reactants and alginate and to follow the conversion of riboflavin into lumichrome. The effect of various scavengers and quenchers on the photosensitized viscosity change was determined. Results: The decrease in viscosity was about 5% and 38% in the absence and presence of sensitizer (riboflavin) respectively after 30 minutes exposure. The main part of the viscosity change did however take place during the initial five minutes of irradiation. This corresponds to the conversion of riboflavin into lumichrome in this system. A combination of glutathion (free radical scavenger) and sodium azid (singlet oxygen quencher) had a strongly retarding effect on the decrease in viscosity when added to the system in the presence of riboflavin. The photosensitized loss of viscosity seems to be related to a combination of polymer degradation and structural changes. Conclusion: The molecular weight and structure of alginate can be strongly affected by light in the presence of a sensitizer. The effect of riboflavin on alginate is most likely due to the formation of singlet oxygen and free radicals resulting from the photodegradation of riboflavin to lumichrome. This demonstrates that photosensitized degradation of alginate has a potential in the design of light activated biopolymer systems. Other sensitizers are now under evaluation in order to optimize the reaction.

• Tesfu, Teame Kiros; Hansen, Finn Knut & Roots, Jaan (2016). Surface characterization of amphoteric and anionic membranes. Universitetet i Oslo.
• Bjørndal, Alexander Raphael Holen; Roots, Jaan & Hansen, Eddy Walther (2014). Optical Biosensors for Glucose. Universitetet i Oslo. Show summary

  GOx was, to the authors knowledge, for the first time successfully immobilized in DGS. The intrinsic fluorescence of GOx was measured in both solution and a sol-gel derived matrix in both the presence and absence of glucose. A setup to measure the fluorescence intensity in a plate array was developed. GOx was, to the authors knowledge, for the first time successfully immobilized in DGS. The intrinsic fluorescence of GOx was measured in both solution and a sol-gel derived matrix in both the presence and absence of glucose. A setup to measure the fluorescence intensity in a plate array was developed.

• Truong, Thuy le; Larsen, Åge Gellein; Holme, Børge; Hansen, Finn Knut & Roots, Jaan (2013). Syndiotactic polypropylene nanocomposites and blends: Morphology, crystallization behavior and tensile properties. Universitetet i Oslo.
• Paul, Jobby; Hansen, Eddy Walther & Roots, Jaan (2013). Ageing of XLPE monitored by solid state1H NMR. Universitetet i Oslo.
• Bjørnsen, Geir; Ulvensøen, Jon Herman; Henriksen, Lars & Roots, Jaan (2010). Patterning of soft polymer films for optical applications. Universitetet i Oslo.
• Zhang, Lili; Hansen, Eddy Walther; Roots, Jaan & Chen, Qun (2009). Solid-state NMR Characterization of Crystallinity and Dynamics in Polyethylene. Universitetet i Oslo.

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