Objectives

Work package 1 deals with the scientific/research achievements involved in the project as well as its budget handling. The latter will be supervised by the Research Committee of the University of Ioannina in collaboration with the PI of the project who will be responsible for keeping the time plan of the project as well as all the necessary updates from the research team concerning scientific achievements according to the work plan and foresee any scientific and/or financial irregularities within the project which should be resolved.

Task 1.1: Project Coordination

Management will be maintained through all WPs for effective outcome of the proposed research. It should also be noticed that research tasks leading to specific deliverables for all work packages are given. The PI will be responsible together with the members of the research group for the successful completion of all tasks, deliverables and milestones as well as supply of consumables and equipment accordingly. The tasks are to monitor progress within the WP prior to completion of the deliverables and will be a vital part of our risk alleviation strategy. These tasks are an “internal” but also official measure of progress and have been included in order to monitor successful outcome and allow any remedial actions to be taken as soon as problems occur, if any, leading to risk and contingency plans as stated in Table 3.4 of the project (given below after the description of the WPs). It will be of significant importance to handle successfully the preparation of reports per deliverable according to the month given in each WP. Also, the hiring of the PhD candidate who is part of the research team will be a first priority and the least requirements for him/her will be: Bachelor or Diploma from Physical Sciences (Chemistry, Physics) or Engineering (Materials Engineer, Chemical Engineer). MSc holder from Physical Sciences (Chemistry, Physics) or Engineering (Materials Engineer, Chemical Engineer). Certified ability of characterizing (in solution and/or bulk) polymers with various characterization techniques. Certified knowledge of handling, using, working in an experimental laboratory for at least two (2) years. Additional skill of PhD candidate: Certified knowledge of controlled polymerization methods and knowledge of “grafting from” and/or grafting to” functionalized surfaces.

Objectives

In this work package the following triblock terpolymers will be synthesized through anionic polymerization and monomer sequential addition: PB1,4-b-PS-b-PDMS, PB1,2-b-PS-b-PDMS, PS-b-PB1,4-b-PDMS and PS-b-PB1,2-b-PDMS as well as the corresponding diblock copolymers of the PS-b-PDMS type for comparison reasons based on the results already reported in the literature for the development of thin films onto various surfaces through the use of homopolymer brushes (PS-OH and PDMS-OH) which as well will be synthesized for comparison reasons. PS: polystyrene, PDMS: poly(dimethylsiloxane), PB1,4: poly(butadiene) with high 1,4 - microstructure (~90-92%) and PB1,2: poly(butadiene) with exclusively 1,2-microstructure (~100%). All samples will be initially characterized molecularly with size exclusion chromatography (SEC), proton nuclear magnetic resonance spectroscopy (1H- NMR) and vapor pressure or membrane osmometry (VPO or MO) through aliquots taken from each polymerization step through the proposed reaction schemes. 

Based on the requirements for today's nanotechnology applications for sub-10nm, the molecular characteristics of the proposed terpolymers, will have total average molecular weight per number in the range of 10,000 g/mol to 15,000 g/mol with the corresponding molecular weight for the PB of any microstructure being in the range of 1,000 g/mol to 2,000 g/mol. The PB block is chosen to be of low molecular weight in order to facilitate the physical adsorption of a very thin layer on the surface of the preferred solid substrate. It will therefore be used as a polymeric brush on a corresponding surface in order to study whether the self-assembly of the remaining two PS and PDMS blocks will be prominent. The sequence of the blocks as well as the type of PB (either PB1,4 or PB1,2) will play a significant role in the proposed research.

Objectives

In the above proposed triblock terpolymers the chemical modification reaction of the PB block will take place through hydroboration/oxidation reactions which lead to the incorporation of –OH functional groups through the initial vinyl content (-1,2 microstructure) on the PB blocks. The vinyl content is only ~8% in the PB1,4 blocks whereas it is almost 100% in the PB1,2 segments. Thorough characterization will take place to verify the successful modification and finally the adsorption/grafting of the modified materials on to various substrates will be tested.

Task 3.1: Chemical Modification of the Triblock Terpolymers of the PB1,4-b-PS-b-PDMS and PS-b-PB1,4-b-PDMS Type

A chemical modification reaction that leads to functionalized intermediates is the hydroboration/oxidation reaction which introduces hydroxyl groups into the double bonds of a polydiene block. The initial hydroboration reaction of the PB vinyl double bonds is achieved by the use of 9-borabicyclo[3.3.1]nonane (9-BBN), followed by oxidation with H2O2/NaOH. The hydroxyl groups introduced by this reaction scheme can be further used for the introduction of other functional groups into the polymer due to the wide range of possible reactions associated with a hydroxyl functionality. Thus, -OH groups can be esterified with an acid chloride or an acid anhydride moiety of another compound making possible the linking of other functional side groups on the main block copolymer chain.

Task 3.2:Chemical Modification of the Triblock Terpolymers of the PB1,2-b-PS-b-PDMS and PS-b-PB1,2-b-PDMS Type

In this action similar approach as that described in Task 3.1 will be adopted following similar modification reactions. The only difference is that the PB blocks are consisting of monomeric units with exclusively vinyl bonds, meaning ~100% 1,2-microstructure. The yield of the modification reaction from vinyl content to –OH groups is again as reported in the literature ~100%.[17]

Task 3.3: Characterization of the Modified Materials

The characterization of the modified samples in order to verify the successful modification in the PB blocks (either ΡΒ1,4 or ΡΒ1,2) will be achieved through the following techniques: size exclusion chromatography (SEC), proton nuclear magnetic resonance spectroscopy (1H- NMR), infra-red spectroscopy (IR), contact angle measurements and differential scanning calorimetry (DSC). We have already verified the ability to successfully modify and thoroughly characterize the modified materials with the aforementioned methods through already published manuscripts in the literature.17,29 It is necessary to verify the high yield of the modification reaction and justify the –OH group functionality for the PB blocks (either PB1,4 or PB1,2).

Task 3.4: Adsorption/Grafting of the Modified Materials onto Surfaces

Various substrates will be used such as glass slides, silicon dioxide (SiO2) and substrates covered with carbon thin films and examine any differences on the final thin film fabricated on the substrate surface. In order to create specific surface properties it is necessary to produce a nanoscopic thin layer on the surface which eventually leads to alternations on the surface appearance and properties, in contradiction with the bulk properties which are being kept constant. The ability to use different segments which can be functionalized through specific modification reactions may lead to direct self-assembled brushes and nanostructures which is the desired outcome of the proposed research.

Objectives

In this workpackage extensive characterization of the initial precursors (non-modified terpolymers) and the modified final terpolymers with various advanced characterization methods in solution and in bulk will take place. In the duration of this work package it should be pointed that according to the submitted letters of intent of renowned researchers to collaborate in the project such as: Prof. C. Ross/MIT, Prof. E. L. Thomas/Rice University, Prof. R.-M. Ho/National Tsing Hua University/Taiwan it will be possible to use advanced equipment from the research group members which do not exist in the host institution (UOI) or generally in Greece.

The use of these instruments could be compensated (through the cost category: Access costs to equipment) from the project and only the UOI research group members will be funded for their travel costs to the foreign Institutions. Actually from the three letters already uploaded in the system it is straightforward that: “The non-funded collaboration.......The measurements will be performed by a member of the scientific/research team of the proposal that will be compensated by the proposal budget. The travel expenses (flights and accommodation) to my Institution for the visiting member will be covered from the proposal of Prof. Avgeropoulos. The inclusion of our research group in scientific publications will be the outcome of this collaboration.” Therefore, it is understood that the three collaborators will help when necessary and the only requirement to use their facilities will be their inclusion and their colleagues aiding in the measurements in scientific publications.

Task 4.1: Characterization in Solution

The following characterization methods in solution are proposed: size exclusion chromatography (SEC), vapor pressure osmometry (VPO), membrane osmometry (MO), low-angle laser light scattering (LALLS), proton nuclear magnetic resonance spectroscopy (1H-NMR), mass spectroscopy measurements (MALDI TOF-MS), contact angle measurements of the modified polymer solutions bearing the hydroxyl groups. For the latter the different behavior in aqueous solutions for the modified materials vs. the initial samples will show substantial differences in contact angle measurements. Through this characterization substantial results will be concluded concerning the correct selection of the proposed triblock terpolymers and their use as polymer brushes through the sacrifice of the PB domains without losing the ability to self-assemble in sub-10 nm nanodomains.

Task 4.2: Characterization in Bulk

Characterization with the following methods is proposed in order to verify the sub-10 nm scale dimensions: atomic force microscopy (AFM), transmission electron microscopy (ΤΕΜ), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). These instruments are available in the PI’s host institution (University of Ioannina). With the first two techniques (AFM and TEM) the structures during microphase separation will be verified in bulk as well as in thin films. It has already been reported in the literature by the PI and his research group that the dependence from the solvent used to prepare the thin films plays a significant role in the adopted morphology. DSC will also verify the microphase separation based on the thermal transitions (especially Tg of PS and PDMS and Tm of PDMS, since the Tg of the PB blocks will be very difficult to observe due to the very low molecular weight (1,000 g/mol to 2,000 g/mol). TGA will also justify the successful grafting of the hydroxyl modified PB segments of the terpolymers through calculation of the grafting density. 

Additional equipment from the collaborating institutions (MIT, Rice University and National Tsing Hua University) is also included in this action. Such instruments are: small-angle X- ray scattering (SAXS) in Synchrotron facility (National Tsing Hua University), scanning probe microscopy, field-emission scanning electron microscopy, in-house SAXS, scanning electron microscopy – focused ion beam (SEM-FIB), multi-beam laser interference lithography setup, etc. which are very useful instruments in order to successfully complete the goals of the proposed research. 

Initial results are already evident in Figure 8, from an already synthesized triblock terpolymer of the PS-b-PB1,4-b-PDMS sequence where an alternating 3-phase 4-layer lamellae structure is evident. The average molecular weights per number for each block are approximately 5.000/1.800/4.000 g/mol for PS/PB1,4/PDMS respectively (total average molecular weight per number for the triblock has been calculated from SEC and VPO equal to 11.000 g/mol). The sample has been cast from toluene (almost a non-preferential solvent for all three blocks) and was not thermally annealed in order to exhibit the highest χ (Flory-Huggins interaction parameter for all possible pairs between the three segments.