| 1. |
- Zorn, Anna-Marie, et al.
(författare)
-
High temperature synthesis of vinyl terminated polymers based on dendronized acrylates : a detailed product analysis study
- 2011
-
Ingår i: POLYMER CHEMISTRY. - : Royal Society of Chemistry (RSC). - 1759-9954 .- 1759-9962. ; 2:5, s. 1163-1173
-
Tidskriftsartikel (refereegranskat)abstract
- The combination of dendrons and high temperature acrylate polymerization represents a viable route to form dendronized macromonomers. Dendronized acrylates based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) were synthesized using dendrimer synthesis and click chemistry (copper catalyzed azide alkyne cycloaddition (CuAAC)). The synthesis was carried out up to the 3rd generation and with a carbon spacer length of 6 or 9 between the acrylic function and the dendron core. These dendronized acrylates were subjected to auto-initiated high temperature acrylate polymerization. The polymerization was performed at 140 degrees C in a 5 wt% solution of hexyl acetate with a 2,2'-azobis(isobutyronitrile) (AIBN) concentration of 5 x 10(-3) g mol(-1). The vinyl terminated polymers were in-depth characterized via size exclusion chromatography (SEC) and size exclusion chromatography coupled to electrospray ionization mass spectrometry (SEC-ESI-MS) to assess the generated product spectrum and the efficiency of the process. The achievable number average molecular weight, M-n, was between 1700 and 4400 g mol(-1). The degree of polymerization, DPn, decreases with increasing generations of the dendronized acrylates from 6.3 to 3.4. The purity of vinyl terminated oligomers containing a geminal double bond is up to 83%, with the dendronized acrylates of the 1st generation providing the best result. Moderate deprotection of the acetonide groups occurred spontaneously during the macromonomer formation process and reached its maximum at generation 3.
|
|
| 2. |
- Boujemaoui, Assya, et al.
(författare)
-
Facile Preparation Route for Nanostructured Composites : Surface-Initiated Ring-Opening Polymerization of epsilon-Caprolactone from High-Surface-Area Nanopaper
- 2012
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 4:6, s. 3191-3198
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, highly porous nanopaper, i.e., sheets of papers made from non-aggregated nanofibrillated cellulose (NFC), have been surface-grafted with poly(epsilon-caprolactone) (PCL) by surface-initiated ring-opening polymerization (SI-ROP). The nanopaper has exceptionally high surface area (similar to 300 m(2)/g). The "grafting from" of the nanopapers was compared to "grafting from" of cellulose in the form of filter paper, and in both cases either titanium n-butoxide (Ti(On-Bu)(4)) or tin octoate (Sn(Oct)(2)) was utilized as a catalyst. It was found that a high surface area leads to significantly higher amount of grafted PCL in the substrates when Sn(Oct)2 was utilized as a catalyst. Up to 79 wt % PCL was successfully grafted onto the nanopapers as compared to filter paper where only 2-3 wt % PCL was grafted. However, utilizing Ti(On-Bu)4 this effect was not seen and the grafted amount was essentially similar, irrespectively of surface area. The mechanical properties of the grafted nanopaper proved to be superior to those of pure PCL films, especially at elevated temperatures. The present bottom-up preparation route of NFC-based composites allows high NFC content and provides excellent nanostructural control. This is an important advantage compared with some existing preparation routes where dispersion of the filler in the matrix is challenging.
|
|
| 3. |
- Bruce, Carl, et al.
(författare)
-
A comparative study of covalent grafting and physical adsorption of PCL onto cellulose
- 2012
-
Konferensbidrag (refereegranskat)abstract
- A growing concern for the environment has, in the past years, directed the research towards a bigger focus on new “greener” materials, such as cellulose-reinforced options. Cellulose is the most abundant organic raw material in the world and it is a versatile material. However, to be able to use it in applications where it is not inherently compatible, a modification is often necessary.1-3 One common method to achieve this modification is to graft polymers onto/from the cellulose chain. This can change the inherent properties of cellulose to attain new properties, such as dimensional stability and water repellency.3 In addition to this, it has been shown that polyectrolytes can be physiosorbed onto charged surfaces.4 Due to this, it is possible to physically modify cellulose by adsorbing a polymer through electrostatic interactions instead of attaching it with a covalent bond.5However, a more detailed investigation concerning differences of covalent and physical attachment of poly(ε-caprolactone) (PCL) onto cellulose, has to the author’s best knowledge not been performed. Therefore, this project aims to compare these two techniques. Covalently bonded PCL was grafted by surface-initiated ring opening polymerization (SI-ROP) from the cellulose. For the adsorption approach, a block copolymer consisting of PCL and a shorter segment of poly(di(methylamino)ethyl methacrylate) (PDMAEMA) was made combining ROP and atom transfer radical polymerization (ATRP). The PDMAEMA-part was then quaternized, which resulted in a cationically charged chain – a polyelectrolyte. This can then be used as an electrostatic linker allowing the PDMAEMA-PCL copolymer to be adsorbed onto the negatively charged cellulose model surface. Finally, differences between the two approaches are evaluated regarding for example surface coverage and grafting/physiosorption efficiency investigated with techniques such as atomic force microscopy (AFM).
|
|
| 4. |
- Bruce, Carl, et al.
(författare)
-
Physical Tuning of Cellulose-Polymer Interactions Utilizing Cationic Block Copolymers Based on PCL and Quaternized PDMAEMA
- 2013
-
Konferensbidrag (refereegranskat)abstract
- In this study, the aim was to prepare and evaluate a block copolymer that can be used as a compatabilizer in cellulose fiber-reinforced biocomposites. It as an amphiphilic block copolymer consisting of poly(ε-caprolactone) (PCL), made with ring-opening polymerization (ROP), and a shorter segment of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) that was synthesized with atom transfer radical polymerization (ATRP). The PDMAEMA-part was made in one single length, while the PCL-part was varied in three different lengths; in total were three block copolymers prepared. In the last step of the synthesis, the PDMAEMA-part was quaternized that turns it into a cationically charged chain – a polyelectrolyte. The block copolymers were then able to form cationic micelles in water, from where they can adsorb, under mild conditions, to anionic surfaces such as silicon oxide and cellulose-model surfaces. This provides the surface with a more hydrophobic character shown with contact angle measurements. Finally, with atomic force microscopy (AFM) force measurements, it was demonstrated that there is a clear entanglement behavior obtained between the block copolymers and a PCL surface at about 60 °C, which is of importance for the information regarding the adhesive interface in a future biocomposite.
|
|
| 5. |
- Bruce, Carl, et al.
(författare)
-
Preparation and evaluation of a block copolymer compatibilizer for biocomposite applications
- 2012
-
Konferensbidrag (refereegranskat)abstract
- In this study, the concept of using a free polymer as a compatibilzer in biocomposite applications has been evaluated with focus on the polymer poly(ɛ-caprolactone) (PCL), commonly used in conventional grafting onto/from cellulose. A block copolymer consisting of PCL and a shorter segment of poly(di(methylamino)ethyl methacrylate) (PDMAEMA) was made combining ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The length of the PDMAEMA-part was kept constant, and the PCL-part was varied in three different lengths, yielding three separate block copolymers. As a final step, the PDMAEMA-part was quaternized, which resulted in cationically charged chains –polyelectrolytes. The charged part could then be used as an electrostatic linker allowing the PDMAEMA-PCL copolymer to be adsorbed onto negatively charged cellulose model surfaces. Finally, these cellulose model surfaces were evaluated regarding for example amount of polymer adsorbed and hydrophobic character, investigated with techniques such as quartz crystal microbalance (QCM) and contact angle measurements.
|
|
| 6. |
- Bruce, Carl, et al.
(författare)
-
Preparation and evaluation of a block copolymer compatibilizer for biocomposite applications
- 2012
-
Konferensbidrag (refereegranskat)abstract
- In this study, a comparison between covalent grafting and physical adsorption of PCL onto a nanocellulose model surface was conducted. For the covalent attachment, surface-initiated ring-opening polymerization (SI-ROP) was performed. For the physical attachment, a charged block copolymer consisting of PCL and quaternized PDMAEMA was synthesized by ROP and ATRP, and adsorbed to the cellulose. Finally, differences in between the two substrates were investigated with techniques such as AFM.
|
|
| 7. |
- Bruce, Carl, et al.
(författare)
-
Preparation and evaluation of triblock copolymers based on poly(2-(dimethylamino)ethyl methacrylate) and poly(epsilon-caprolactone)
- 2013
-
Ingår i: Abstracts of Papers of the American Chemical Society. - 0065-7727. ; 245, s. 613-POLY-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this work, the preparation of two block copolymers based on poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(ε-caprolactone) (PCL) has been conducted, creating the triblock copolymers PDMAEMA-b-PCL-b-PDMAEMA and PCL-b-PDMAEMA-b-PCL. The PDMAEMA-part was then quaternized, to give polyelectrolytes with either one or two charged block(s). Subsequently, differences in properties were studied in the solid state, in solution and in water dispersion with techniques including differential scanning calorimetry, size exclusion chromatography and dynamic light scattering.
|
|
| 8. |
- Bruce, Carl, et al.
(författare)
-
Preparation and evaluation of well-defined di- and triblock copolymers based on poly[2-(dimethylamino)ethyl methacrylate] and poly(ε-caprolactone)
- 2014
-
Ingår i: ACS National Meeting.
-
Konferensbidrag (refereegranskat)abstract
- In this work, di- and triblock copolymers based on poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(ε-caprolactone) (PCL) have been prepared. The PDMAEMA length was kept constant for both di- and triblock copolymers, while in the diblock copolymers the PCL length was varied in three different lengths, yielding three separate block copolymers. For the triblock blockcopolymers, on the other hand, also the PCL blocks were of the same length yielding one ABA- and one BAB-type block copolymer. In the next step, the PDMAEMA-part was quaternized to yield polyelectrolytes with either one or two charged block(s). In the final step, difference in adsorption behavior onto a negatively charged cellulose surface and subsequent alteration of surface properties was investigated. Overall, the polymers were evaluated in solid state, in solution, in water dispersion, and on cellulose surfaces with techniques including differential scanning calorimetry, size exclusion chromatography, dynamic light scattering and quartz crystal microbalance.
|
|
| 9. |
- Bruce, Carl, 1985-
(författare)
-
Surface Modification of Cellulose by Covalent Grafting and Physical Adsorption for Biocomposite Applications
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is an increasing interest to replace fossil-based materials with renewable alternatives. Cellulose fibers/nanofibrils (CNF) are sustainable options since they are biobased and biodegradable. In addition, they combine low weight with high strength; making them suitable to, for example, reinforce composites. However, to be able to use them as such, modifications are often necessary. This study therefore aimed at modifying cellulose fibers, model surfaces of cellulose and CNF. Cellulose fibers and CNF were thereafter incorporated into composite materials and evaluated.Surface-initiated ring-opening polymerization (SI-ROP) was performed to graft ε-caprolactone (ε-CL) from cellulose fibers. From these fibers, paper-sheet biocomposites were produced that could form laminate structures without the need for any addition of matrix polymer.By combining ROP and atom transfer radical polymerization (ATRP), diblock copolymers of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and PCL were prepared. Quaternized (cationic) PDMAEMA, allowed physical adsorption of block copolymers onto anionic surfaces, and, thereby, alteration of surface energy and adhesion to a potential matrix. Furthermore, the architecture of block copolymers of PCL and PDMAEMA was varied to investigate effects on morphology/crystallinity and adsorption behavior. In addition, poly(butadiene) was also evaluated as the hydrophobic block in the form of cationic and anionic triblock copolymers.Polystyrene (PS) was covalently grafted from CNF and used as reinforcement in PS-based composites. In an attempt to determine stress transfer from matrix to CNF, a method based on Raman spectroscopy was utilized.Covalent grafting and physical adsorption of PCL from/onto CNF were compared by incorporating modified CNF in PCL matrices. Both approaches resulted in improved mechanical properties compared to unmodified CNF, but even at low amounts of modified CNF, covalent grafting gave tougher materials and indicated higher interfacial adhesion.
|
|
| 10. |
- Bruce, Carl, et al.
(författare)
-
Well-defined ABA- and BAB-type block copolymers of PDMAEMA and PCL
- 2014
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:49, s. 25809-25818
-
Tidskriftsartikel (refereegranskat)abstract
- Triblock copolymers of ABA- and BAB-type consisting of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA, A) and poly(epsilon-caprolactone) (PCL, B) have successfully been prepared. PDMAEMA-b-PCL-b-PDMAEMA (ABA) and PCL-b-PDMAEMA-b-PCL (BAB) were synthesised by a combination of ring-opening polymerisation of epsilon-CL, atom transfer radical polymerisation of DMAEMA and end-group conversion, performed through either acylation or azide-alkyne "click" chemistry. All samples were analysed by size exclusion chromatography where it was found that the evaluation of PDMAEMA-containing polymers was difficult due to the thermoresponsivity of PDMAEMA, affecting the solubility of the polymer in the temperature range at which the SEC was operated. From differential scanning calorimetry measurements it was shown that the crystallinity could be altered by changing the order of the blocks; with PDMAEMA as the outer block (ABA), the inherent crystallinity of PCL was destroyed while with PCL as the outer block (BAB), the degree of crystallinity was in the same proximity as for a PCL homopolymer.
|
|
