| 1. |
- Asem, Heba, 1987-, et al.
(författare)
-
Polymeric Nanoparticles Explored for Drug-Delivery Applications
- 2018
-
Ingår i: Gels and Other Soft Amorphous Solids. - Washington, DC : American Chemical Society (ACS). - 9780841233164 ; , s. 315-331
-
Bokkapitel (refereegranskat)abstract
- The main drawback of conventional chemotherapeutics is their non-specific distribution in the body which causes serious side effects to healthy cells. As a consequence, the drug concentration reaching the tumor is reduced, resulting in suboptimal therapeutic efficacy. The discovery that polymer-based nanomaterials can be used for controlled drug delivery systems offers well-defined reservoirs for a wide spectrum of pharmaceutical agents, with the ability to reduce the toxic response. The most widely explored polymeric nanocarriers, including biodegradable polymers, amphiphilic copolymers and polymers that form unimolecular micelles, are discussed in this brief chapter.
|
|
| 2. |
|
|
| 3. |
- Boujemaoui, Assya, et al.
(författare)
-
Polycaprolactone Nanocomposites Reinforced with Cellulose Nanocrystals Surface-Modified via Covalent Grafting or Physisorption : A Comparative Study
- 2017
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:40, s. 35305-35318
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work, cellulose nanocrystals (CNCs) have been surface-modified either via covalent grafting or through physisorption of poly(n-butyl methacrylate) (PBMA) and employed as reinforcement in PCL. Covalent grafting was achieved by surface-initiated atom transfer radical polymerization (SI-ATRP). Two approaches were utilized for the physisorption: using either micelles of poly(dimethyl aminoethyl methacrylate)-block-poly(n-butyl methacrylate) (PDMAEMA-b-PBMA) or latex nanoparticles of poly(dimethyl aminoethyl methacrylate-co-methacrylic acid)-block-poly(n-butyl methacrylate) (P(DMAEMA-co-MAA)-b-PBMA). Block copolymers (PDMAEMA-b-PBMA)s were obtained by ATRP and subsequently micellized. Latex nanoparticles were produced via reversible addition-fragmentation chain-transfer (RAFT) mediated surfactant-free emulsion polymerization, employing polymer-induced self-assembly (PISA) for the particle formation. For a reliable comparison, the amounts of micelles/latex particles adsorbed and the amount of polymer grafted onto the CNCs were kept similar. Two different chain lengths of PBMA were targeted, below and above the critical molecular weight for chain entanglement of PBMA (M-n,M-c similar to 56 000 g mo1(-1)). Poly(epsilon-caprolactone) (PCL) nanocomposites reinforced with unmodified and modified CNCs in different weight percentages (0.5, 1, and 3 wt %) were prepared via melt extrusion. The resulting composites were evaluated by UV-vis, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and tensile testing. All materials resulted in higher transparency, greater thermal stability, and stronger mechanical properties than unfilled PCL and nanocomposites containing unmodified CNCs. The degradation temperature of PCL reinforced with grafted CNCs was higher than that of micelle-modified CNCs, and the latter was higher than that of latex-adsorbed CNCs with a long PBMA chain length. The results clearly indicate that covalent grafting is superior to physisorption with regard to thermal and mechanical properties of the final nanocomposite. This unique study is of great value for the future design of CNC-based nanocomposites with tailored properties.
|
|
| 4. |
- Boujemaoui, Assya, et al.
(författare)
-
Preparation and characterization of functionalized cellulose nanocrystals
- 2015
-
Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 115, s. 457-464
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a series of functional nanocrystals (F-CNCs) was successfully produced by an efficient preparation method, combining acid hydrolysis and Fischer esterification with various organic acids. Functionalities such as ATRP initiators, double bonds, triple bonds, and thiols could be incorporated on CNCs. Surface modification was confirmed by FT-IR, XPS, and elemental analysis. Physical properties of FC-NCs were assessed by AFM, XRD and TGA. Moreover, ATRP initiator functionalized CNCs were utilized to graft poly(methyl methacrylate) via ATRP, thiol functionalized CNCs were reacted with Ellman's reagent to determine the thiol content and dye disperse red 13 was attached to alkyne functionalized CNCs to estimate the propiolate content. The herein presented method is a highly versatile and straightforward procedure for the preparation of F-CNCs which is believed to be a better alternative for the commonly utilized, extensive, multistep, and time consuming post functionalization methods.
|
|
| 5. |
- Boujemaoui, Assya, et al.
(författare)
-
SI-RAFT/MADIX polymerization of vinyl acetate on cellulose nanocrystals for nanocomposite applications
- 2016
-
Ingår i: Polymer. - : Elsevier. - 0032-3861 .- 1873-2291. ; 99, s. 240-249
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work, poly(vinyl acetate) grafted cellulose nanocrystals (CNC-g-PVAc) were prepared via surface initiated reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthates (SI-RAFT/MADIX) polymerization. Successful grafting of PVAc from CNC was confirmed by FT-IR and TGA analysis. PVAc nanocomposites reinforced with CNC-g-PVAc, as well as pristine CNC for comparison, of different weight percentages (0.5, 1, 3 and 5 wt%) of CNC were prepared via solvent casting. The PVAc reinforced with CNC-g-PVAc resulted in higher transparency and improved mechanical properties compared with unmodified CNC nanocomposites. The addition of 5 wt% CNC-g-PVAc increased the modulus of neat PVAc with as much as 154%. The proposed SI-RAFT/MADIX on CNC could be applied to wide range of monomers, and it is believed to be an efficient and robust method for CNC functionalization, thus expanding the potential applicability of CNC.
|
|
| 6. |
- Boujemaoui, Assya, 1983-
(författare)
-
Surface Modification of Nanocellulose towards Composite Applications
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanocelluloses have attracted great interest during recent decades owing to their renewability, abundancy and remarkable physical and mechanical properties. The aim of this work was to investigate new strategies for surface modification and functionalization of nanocelluloses and their subsequent incorporation in polymer-host matrices.Nanocomposites of cellulose nanofibrils (CNF) and polycaprolactone (PCL) were produced by employing CNF nanopaper (NP) as a template and surface-initiated ring-opening polymerization (SI-ROP) of ε-caprolactone (ε-CL). SI-ROP of ε-CL from filter paper (FP) was also carried out for comparison. A larger amount of PCL was grafted from NP than from FP. The grafted NP had stronger mechanical properties than neat PCL.Cellulose nanocrystal (CNC)-reinforced polyvinyl acetate (PVAc) nanocomposites were also investigated. CNC were modified via “SI-reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthate” (SI-RAFT/MADIX) polymerization of vinyl acetate (VAc). The resulting nanocomposites exhibited improved mechanical performance than the unmodified CNC.It is generally agreed that covalent grafting is superior to physical adsorption for the modification of a reinforcing agent. However, this hypothesis has never been thoroughly investigated. CNC was modified either through covalent grafting or through physical adsorption of poly(butyl methacrylate) (PBMA). Both methods resulted in improved mechanical performance than that of pure PCL or PCL containing unmodified CNC. However, covalent grafting gave the best mechanical performance even at high relative humidity.Functionalized CNC (F-CNC) were obtained through a versatile methodology employing organic acids bearing a functional group were employed for the simultaneous acid hydrolysis and esterification of cellulose fibers. This provided a facile route for the preparation of F-CNC.
|
|
| 7. |
- Bruce, Carl, et al.
(författare)
-
Paper-sheet biocomposites based on wood pulp grafted with poly(epsilon-caprolactone)
- 2015
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 132:23
-
Tidskriftsartikel (refereegranskat)abstract
- Kraft pulp fibers were used as substrates for the grafting of poly(epsilon-caprolactone) (PCL) from available hydroxyl groups through ring-opening polymerization, targeting three different chain lengths (degree of polymerization): 120, 240, and 480. In a paper-making process, paper-sheet biocomposites composed of grafted fibers and neat pulp fibers were prepared. The paper sheets possessed both the appearance and the tactility of ordinary paper sheets. Additionally, the sheets were homogenous, suggesting that PCL-grafted fibers and neat fibers were compatible, as demonstrated by both Fourier transform infrared spectroscopy microscopy and through dye-labeling of the PCL-grafted fibers. Finally, it was shown that the paper-sheet biocomposites could be hot-pressed into laminate structures without the addition of any matrix polymer; the adhesive joint produced could even be stronger than the papers themselves. This apparent and sufficient adhesion between the layers was thought to be due to chain entanglements and/or co-crystallization of adjacent grafted PCL chains within the different paper sheets. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42039.
|
|
| 8. |
- Brännström, Sara, et al.
(författare)
-
Biobased UV-curable coatings based on itaconic acid
- 2017
-
Ingår i: Journal of Coatings Technology Research. - : Springer-Verlag New York. - 1945-9645 .- 1547-0091 .- 1935-3804. ; 14:4, s. 851-861
-
Tidskriftsartikel (refereegranskat)abstract
- A series of renewable unsaturated polyesters were synthesized from itaconic acid (IA), succinic acid, and 1,4-butanediol by solvent-free polycondensation. Previous studies utilizing IA to make polyesters for coating applications have shown great potential; however, the curing and material properties have not been investigated in detail. The aim of this study was to investigate how the curing is affected by the amount of unsaturations and how well itaconate-based polyesters crosslink without the addition of any other unsaturated monomers or reactive diluents. The chemical structures of the polyesters were confirmed with FTIR, 1 HNMR, and THF-SEC. The degree of curing was studied with FTIR, and the mechanical properties of the crosslinked polyesters were evaluated with DMA, pendulum hardness, and microindentation. The degree of curing was found to be up to 75%, and furthermore, it was found that the final mechanical properties of the crosslinked coatings could be tuned by modifying the IA content in the monomer composition. The results from DMA showed that there is a clear trend between mechanical properties and crosslinking density.
|
|
| 9. |
- Brännström, Sara, et al.
(författare)
-
Enzymatically Synthesized Vinyl Ether-Disulfide Monomer Enablingan Orthogonal Combination of Free Radical and Cationic Chemistry toward Sustainable Functional Networks
- 2019
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:3, s. 1308-1316
-
Tidskriftsartikel (refereegranskat)abstract
- This work demonstrates a versatile and environmentally friendly route for the development of new orthogonal monomers that can be used for postfunctionalizable polymer networks. A monomer containing both vinyl ether (VE) and cyclic disulfide moieties was synthesized via enzyme catalysis under benign reaction conditions. The bifunctional monomer could be polymerized to form macromolecues with differing architectures by the use of either cationic or radical photo polymerization. When cationic polymerization was performed, a linear polymer was obtained with pendant disulfide units in the side chain, whereas in the presence of radical initiator, the VE reacted with the disulfide to yield a branched structure. The monomer was thereafter used to design networks that could be postfunctionalized; the monomer was cross-linked with cationic initiation together with a difunctional VE oligomer and after cross-linking the unreacted disulfides were coupled to RhodamineVE by radical UV-initiation.
|
|
| 10. |
- Brännström, Sara, 1991-
(författare)
-
Exploring bio-based monomers for UV-curable polymer networks
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increased environmental awareness and concern has led to a high demand for sustainable, bio-based materials. Consequently, there is a need for research and development of new bio-based polymeric materials that can be synthesized via routes eliminating excessively toxic reactants and by-products. The work presented in this thesis has focused on the utilization of catalysis, mainly enzymatic, and photopolymerization in order to create efficient synthesis of polymeric networks from bio-based monomers.Polyesters from bio-based monomers have been polymerized in bulk and thereafter crosslinked by UV initiation to yield polymer networks with tunable properties. The synthesis was also studied more in detail by varying the different types of catalysts and comparing their effect on the polymer products. Polyesters are a promising class of polymers that can be made from bio-based resources due to the wide range of available bio-based carboxylic acids and alcohols that can be combined to yield many polymers with different properties. However, the synthesis of polyesters is rather time-consuming in order to reach high conversions.As a more efficient alternative, short chain esters monomers and oligomers that have vinyl ether (VE) functionalities were developed. These VE-esters can be synthesized partly from bio-based resources, such as acids, fatty acids and diols, and their synthesis is efficient with enzymatic catalysis. The VE functionality provides a reactive group which can be polymerized rapidly with cationic polymerization. In general, the vinyl ether-esters can be synthesized in less than one hour and crosslinked within a few minutes, which is significantly faster than traditional polyester-synthesis and crosslinking. The enzymatic synthesis of vinyl ether esters also provided a method for developing monomers with orthogonal functionality which was explored by developing functionalizable materials with a variety of macromolecular architectures.
|
|
