| 1. |
- Ranucci, E., et al.
(author)
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New ester and lactone end-functionalized N-vinyl-2-pyrrolidinone oligomers
- 2000
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In: Macromolecular Chemistry and Physics. - 1022-1352 .- 1521-3935. ; 201:12, s. 1219-1225
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Journal article (peer-reviewed)abstract
- New oligomers of N-vinyl-2-pyrrolidinone functionalized at one end with either ester or lactone functions were obtained by radical polymerization in the presence of different ester (methyl isobutyrate and methyl phenylacetate) and lactone (epsilon-caprolactone, delta-valerolactone and gamma-btyrolactone) compounds as chain transfer agents. The oligomeric samples obtained were characterized in terms of molecular weight and molecular weight distribution by means of analytical size exclusion chromatography (SEC), using purposely synthesized poly(N-vinyl-2-pyrrolidinone) standards. The chain transfer constant C-tau of either methyl isobutyrate, delta-valerolactone, or gamma-butyrolactone towards N-vinyl-2-pyrrolidinone were determined with the help of the known cumulative number-average degree of polymerization (X) over bar(n) and monomer conversion Y-t of the samples during the reaction.
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| 2. |
- Hakkarainen, Minna, et al.
(author)
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Heterogeneous biodegradation of polycaprolactone - Low molecular weight products and surface changes
- 2002
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In: Macromolecular Chemistry and Physics. - 1022-1352 .- 1521-3935. ; 203:11-okt, s. 1357-1363
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Journal article (peer-reviewed)abstract
- Gas chromatography-mass spectrometry (GC-MS) analysis showed that caprolactone, 6-hydroxyhexanoic acid, cyclic dimer and cyclic trimer were rapidly assimilated from the surface of polycaprolactone (PCL) films aged in mineral medium inoculated with a mixed culture of compost microorganisms. The degradation in biotic medium proceeded heterogeneously and scanning electron micrographs revealed the formation of parallel grooves, spherical and non-spherical holes in the films. The parallel grooves seen in the scanning electron micrographs after 14 d suggest that the degradation starts preferentially at the amorphous regions. At longer time scales, even the crystalline regions are degraded producing large spherical and non-spherical holes. Comparison of the degradation of melt-pressed and film-blown films made from the same PCL granules in different biotic and abiotic environments showed that both the type of microorganism used and the initial morphology of the films influence the surface erosion pattern and biodegradation mechanism. Rapid degradation and molecular weight decrease required the combined effect of temperature and microorganisms obtained during a biodegradation process, such as composting.
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| 3. |
- Achtel, Christian, et al.
(author)
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Dissolution capacity of novel cellulose solvents based on triethyloctylammonium chloride
- 2017
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In: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 218:21
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Journal article (peer-reviewed)abstract
- Dissolution of cellulose from various sources (microcrystalline cellulose and different dissolving grade pulp fibers) is investigated in solvent systems based on triethyl(n-octyl)ammonium chloride (N2228Cl). Clear cellulose solutions are obtained with N2228Cl in a variety of solvents, e.g., dimethyl sulfoxide, N,N-dimethylacetamide, and acetone. It is possible to prepare clear cellulose solutions from pulp fibers with concentrations up to 15 wt%. However, it is found that the cellulose is degraded, especially when neat (i.e., molten) N2228Cl is used as a solvent. The present work includes comprehensive rheological characterization of the cellulose solutions, both with shear and extensional rheology. In most cases, the viscosity values are low (complex viscosities below 100 Pa s for 5–10 wt% dissolved cellulose), and the solutions show more Newtonian than viscoelastic behavior.
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| 4. |
- Alexakis, Alexandros Efraim, et al.
(author)
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Modification of CNF‐Networks by the Addition of Small Amounts of Well‐Defined Rigid Cationic Nanolatexes
- 2022
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In: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 224:1, s. 2200249-2200249
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Journal article (peer-reviewed)abstract
- Cellulose nanofibril (CNF)-networks are modified by the addition of small amounts (below 10 wt%) of well-defined cationic nanolatexes synthesized through reversible addition–fragmentation chain-transfer-mediated polymerization-induced self-assembly (PISA). Minute amounts of nanolatex inclusions lead to increased tensile and shear moduli, indicating that nanolatexes can act as bridging-points between CNFs. At higher nanolatex content, this stiffening effect is lost, likely due to interactions between nanolatexes leading to plasticization. The influence of nanolatex content and size on interparticle distance is discussed and is used as a tool to understand the effects observed in macroscopic properties. Upon annealing, the stiffening effect is lost due to the softening of the nanolatexes, indicating that the core–shell morphology is a prerequisite for this effect. These systems form a versatile platform to develop fundamental insights into complex condensed colloidal systems, to ultimately aid in the development of new sustainable material concepts.
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| 5. |
- Andac, M, et al.
(author)
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Poly(hydroxyethyl methacrylate)-based macroporous hydrogels with disulfide cross-linker
- 2008
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In: Macromolecular Chemistry and Physics. - : Wiley. - 1521-3935 .- 1022-1352. ; 209:6, s. 577-584
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Journal article (peer-reviewed)abstract
- Biodegradable supermacroporous PHEMA cryogels were produced by combining two cross-linkers, poly(ethylene glycol) diacrylate and a newly developed disulfide water soluble crosslinker, N,N'-bis(methacryloyl)-L-cystine. The biodegradable PHEMA cryogels were prepared with gel fraction yields up to 70% and were characterized by highly interconnected pores of micrometer size and good mechanical stability. When subjected to reductive agents like DTT, the biodegradable PHEMA cryogels disintegrated into small pieces. The rate of disintegration was controlled by the crosslinking density in the cryogels and the DTT concentration.
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| 6. |
- Andersson, Mattias, 1985, et al.
(author)
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Influence of Molecular Weight on the Creep Resistance of Almost Molten Polyethylene Blends
- 2018
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In: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 219:3
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Journal article (peer-reviewed)abstract
- The most common route to improve the creep resistance of low density polyethylene (LDPE) is crosslinking, which however results in volatile decomposition products that must be removed. Blends of LDPE and an additive-like amount of a linear polyethylene are found to offer improved creep resistance. Above the melting temperature of LDPE, T m ≈ 111 °C, a load-bearing network of higher-melting crystallites—connected through tie chains and trapped entanglements—provides additional form stability. The molecular weight of the linear polyethylene is found to be critical for the ability to arrest creep, which is correlated with the probability of tie chain formation as well as cocrystallization of the two polyethylenes. A number of high-density polyethylenes (HDPE) and one ultrahigh molecular weight polyethylene (UHMW-PE) are explored. For blends of LDPE and 2 wt% of the linear polyethylene, an HDPE with a weight-average molecular weight M w of 16 kg mol −1 is found to be sufficient to arrest creep at 115 °C. Further improvement in terms of creep resistance is obtained in case of UHMW-PE with creep fracture occurring only at a stress of 12 kPa at 115 °C. (Figure presented.).
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| 7. |
- Andersson, Per
(author)
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Pressure dependence of the thermal conductivity of some polyamides
- 1976
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In: Macromolecular Chemistry and Physics. - Basel : Wiley. - 1022-1352 .- 1521-3935. ; 177, s. 271-277
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Journal article (peer-reviewed)abstract
- The pressure dependence of the thermal conductivities of five polyamides (nylons) have been determined ina cylindrical geometry at 300 K and in the pressure range 0-25 kbar. The conductivities increase strongly with pressure, the values at 25 kbar being higher by the factors 1,83, 1,90, 2,07, and 2,03 for, respectively, nylon 66, nylon 610, nylon 6, nylon 11, and nylon 12, than those at atmospheric pressure. The results are compared with other exerimental results and with theoretical calculations. The difference in conductivity response to pressure between the different varieties is discussed.
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| 8. |
- Bini, Kim, 1987, et al.
(author)
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Synthesis and Characterization of Isoindigo-Based Polymers with Thermocleavable Side Chains
- 2018
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In: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 219:7
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Journal article (peer-reviewed)abstract
- Stability of bulk heterojunction films for organic solar cells is a critical factor for commercial viability. One method to stabilize these films is to include cleavable side chains, which reduce the solubility of the polymers when removed. In order to study the stabilizing effect of cleavable side chains, a series of random copolymers using isoindigo with 0, 10, 20, 50, and 100% thermally cleavable side chains based on the tert-butyloxycarbonyl (t-BOC) group are synthesized. The polymers show a distinct one-step thermal cleavage of the side chains, with no separable dealkylation and decarboxylation steps. The thermal stability in film is studied with transmission electron microscopy and atomic force microscopy. The polymer with all t-BOC side chains on isoindigo significantly improves thermal stability with regard to crystal growth and phase separation in film. These results suggest BOC-substitution can be used for large scale processing to produce insoluble polymer films with a high degree of thermal stability.
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| 9. |
- Brännström, Sara, et al.
(author)
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Tailoring Thermo-Mechanical Properties of Cationically UV-Cured Systems by a Rational Design of Vinyl Ether Ester Oligomers using Enzyme Catalysis
- 2018
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In: Macromolecular Chemistry and Physics. - : WILEY-V C H VERLAG GMBH. - 1022-1352 .- 1521-3935. ; 219:21
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Journal article (peer-reviewed)abstract
- There is a demand for new sustainable polymeric materials. Vinyl ethers are, in this context, attractive oligomers since they polymerize fast, are non-toxic, and can be polymerized under ambient conditions. The availability of vinyl ether oligomers is, however, currently limited due to difficulties in synthesizing them without using tedious synthesis routes. This work presents the synthesis of a series of vinyl ether ester oligomers using enzyme catalysis under solvent-free conditions and the subsequent photoinduced cationic polymerization to form polymer thermosets with T(g)s ranging from -10 to 100 degrees C. The whole process is very efficient as the synthesis takes less than 1 h with no need for purification and the crosslinking is complete within 2 min.
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| 10. |
- Carlmark, Anna
(author)
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Tailoring cellulose surfaces by controlled polymerization methods
- 2013
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In: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 214:14, s. 1539-1544
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Journal article (peer-reviewed)abstract
- Cellulose, with its excellent mechanical properties and low weight, would be highly advantageous to employ in bioplastics and biocomposites applications. However, to expand the utilization of cellulose beyond its traditional uses, a modification of the fiber surface is often a prerequisite. One approach is to graft polymer chains on the surface in order to compatibilize the fibers with a non-polar polymer matrix or to introduce functionalities. By exploiting controlled polymerization methods such as ATRP, RAFT, ROP, and ROMP, the surface of the fibers can be carefully tailored. Herein, an overview on controlled, heterogeneous grafting of cellulose fibers and fibrils employing both "grafting from" and "grafting to" methodologies is provided, focusing on the latest findings.
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