<p>This thesis summarizes experimental and theoretical studies on N-vinylformamide (NVF) free radical polymerization and the synthesis and evaluation of cationic grafted copolymers for flocculation purpose. The free radical polymerization of N-vinylformamide was studied in bulk and aqueous solution processes. The molar heat of reaction for NVF polymerization was measured to be 79.4 kJ/mo!. The polymerization kinetics, including the conversion versus time, molecular weight and molecular weight distribution, was examined systematically. Significant "gel effect" was observed in bulk and solution polymerization when the monomer concentration was over 40wt% (5.63 moI/L). A semi-empirical model based on the free volume theory was proposed to describe both the bulk and solution polymerizations. It was also confirmed that amide group provided crosslinking points that formed PNVF gel during NVF free radical polymerization. The subsequent acidic and basic hydrolysis to convert PNVF to PV Am was also studied systematically. The effect of temperature, polymer/acid (or base) ratios and polymer concentrations were examined. Two methods were used to synthesize cationic grafted copolymers for flocculation purposes. In the first method, NVF monomer was copolymerized with two cationic poly dimethylaminoethyl methacrylate (polyDMAEMA) methyl chloride macromonomers to produce a series of comb-grafted copolymers with different cationic contents. One cationic macro monomer had a molecular weight of 14,100 (50 repeating units) and the other had a molecular weight of 28,200 (100 repeating units). The copolymerization reactivity ratio (r₁) of the comonomer pair (NVF(M₁)-macromonomer(M₂)) was determined to be 3.82 and 6.39 for the two macromonomers with 50 and 100 repeating units. The flocculation performance of the graft copolymers was tested on a TiO₂ aqueous dispersion model system. The graft copolymers were found to be more effective in flocculation than their random linear counterparts. In the second method, poly diallydimethyl ammonium chloride (polyDADMAC) was grafted onto polyacrylamide (PAM) using a mini-mixer in melts with an organic peroxide, Lupersol 130. This process resembled reactive processing usually carried out at a larger scale in extruders to handle highly viscous polymer reactions. The grafting was confirmed and successful. However, severe gelation problem with PAM that occurred during the process hampered the grafting efforts. Parallel to these studies based on experimental data, a theoretical model was derived to describe the bivariate distribution of molecular weight and branching density for comb-grafted copolymers. This model was based on the random grafting of pre-formed side chains onto backbones (grafting-onto) mechanism. However, it is also applicable to the comb polymers synthesized by grafting-from and grafting-through mechanisms as long as the inclusion of the branching point is a random process.</p> / Doctor of Philosophy (PhD)

<p>Atom transfer radical polymerization (ATRP), a transition metal-mediated living radical polymerization, has been developed as a powerful tool for synthesizing polymers of controlled structure, but its catalyst residue remains challenging. Described in this thesis is a comprehensive study on the ATRP applications in macromonomer preparation and the solutions to its catalyst residue problem by catalyst supporting. A novel continuous process for the production of polymers and block copolymers with controlled molecular weights has also been developed using packed column reactor technologies. New versatile vinyl-containing initiators, 2'-vinyloxyethyl 2-bromoisobutyrate (VBIB) and 3'-vinyloxylpropyl trichloroacetamide (VTCA), were screened for the macromonomer synthesis of different vinyl monomer types by ATRP. Polymethacrylate and polystyrene macromonomers of well-controlled molecular weights were obtained without consumption of the initiators' vinyl moieties at monomer conversions lower than 80%. However, the ATRP of acrylates started to consume the vinyl moieties at medium conversions. Therefore, the polymerization of acrylates must be terminated at an early stage in order to obtain their macromonomers. Three catalyst supporting systems have been developed to solve the catalyst contamination problem for batch ATRP. Firstly, the CuBr/HMTETA complex was supported onto silica gel by physical adsorption for ATRP of MMA in toluene. The supported complex mediated a living polymerization of MMA. The recycled catalysts had a high retention of catalyst activity and improved control over the polymer molecular weights. Secondly the catalyst was immobilized on silica gel by covalent bonding for polar solvent/monomer systems. In this supporting method, the supporting spacer length was found to strongly affect the catalyst activity and control of the polymerization. The catalyst supported via three-unit PEG had highest activity and regulated the polymerization best. Longer or shorter spacer deteriorated catalyst activity and control of polymerization. Thirdly, the catalyst was grafted onto soluble and recoverable PE and PE-b-PEG supports to overcome the adverse effects of insoluble support. Catalyst directly grafted on the long PE chains had low activities, poor control over polymerization and low retention of the catalyst activity upon recycling. Using PEG as spacer to graft the catalyst onto the PE support minimized these adverse effects of the PE support. PE₂₅-PEG₄-TEDETA-CuBr effectively mediated the ATRP of MMA, and retained 90% activity of the fresh catalyst upon recycling with good polymer molecular weight control. Catalyst recycling for batch ATRP was found laborious and time-demanding. A continuous ATRP using column reactors packed with silica gel supported CuBr/HMTET A was developed for homo- and block-copolymerization of MMA. The reactor showed good stability in both catalyst activity and molecular weight control of resulting PMMA. The polymerization in the reactor was still a living process. Thus, adjusting the MMA flow rate, which determined the monomer conversion, readily changed the molecular weight of PMMA. The block copolymerization of MMA with nbutyl methacrylate (nBMA) was carried out using two reactors in series. The produced block copolymers had little contamination of PMMA prepolymer. The chain length of nBMA block could be adjusted by the flow rate of nBMA in the second reactor.</p> / Doctor of Philosophy (PhD)

<p>Cationic macromonomers of poly [2-(dimethylamino) ethyl methacrylate dimethyl sulfate] polyDMAEMA-DMS) were synthesized by both living nitro-anionic polymerization with a novel capping technique and atom-transfer radical polymerization (ATRP). The macromonomers were copolymerized with acrylamide to give well-defined comb-branched polyelectrolytes having polyacrylamide (PAM) backbone and polyDMAEMA-DMS side chains by free radical processes. First, the radical mechanism involved in ATRP was investigated using an electron spin resonance (ESR) spectrometer and a differential scanning calorimeter (DSC). Poly (ethylene glycol) dimethacrylate (PEGDMA) was used as a model system for this purpose of mechanism elucidation. The network-forming feature of the system imposed diffusion limitations to radical deactivation reactions and thus allowed us to directly observe the radical intermediates during the polymerization by the first time. The polyDMAEMA macromonomers bearing terminal allyl moieties were synthesized by the A TRP method using allyl-containing organic halide as initiator. The polyDMAEMA macromonomers with styrenic end groups were prepared by the living nitro-anionic polymerization. A novel capping technique was developed to improve the initiator efficiency in the anionic polymerization. The polyDMAEMA macromonomers were quatemized with dimethyl sulfate yielding cationic polyDMAEMA-DMS macromonomers. The copolymerization of acrylamide with polyDMAEMA-DMS macromonomers was conducted using 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AlBA) as free radical initiator in aqueous solution. The reactivity ratios in copolymerization were measured for the two series of cationic macromonomers with terminal styrenic or allyl groups. PolyDMAEMA-DMS macromonomer with styrenic end group was found to have a much higher reactivity than acrylamide. It was attributed to the hydrophobic characteristic of styrenic group and the micelle formation of the macromonomer in aqueous media. In contrast, the PolyDMAEMA-DMS macromonomer with terminal allyl group had lower reactivity than acrylamide. This difference in reactivities caused a chemical composition drifting during the copolymerization. A semi-batch method was used to control the copolymer composition for synthesizing comb-branched cationic polyelectrolytes.</p> / Doctor of Philosophy (PhD)

<p>The methanation of carbon monoxide and carbon dioxide was studied over Raney nickel. The catalyst was characterized by chemisorption techniques. A differential plug-fIow reactor was used to obtain kinetic data. The reaction rates were investigated as a function of temperature, reactants and products concentrations. The power rate law was found inadequate in representing the kinetic data of carbon dioxide methanation. The orders of reaction for hydrogen and carbon monoxide were obtained. Carbonaceous species were found on the catalyst surface after methanation reaction, which could react with hydrogen give methane. Multilayers of carbon species were deposited on the catalyst surface during CO methanation; less than a monolayer was found when carbon dioxide was used as feed. The effects of reaction conditions on the amount of residual carbon was also investigated.</p> <p>The data in general agrees with a mechanism involving the hydrogenation of carbonaceous species as the rate determining step. The differences between CO and CO₂ methanations were also discussed.</p> <p>The carbon chain growth process in the Fischer-Tropsch synthesis was simulated using available data in the literature. The simulation was done by representing the hydrocarbon chains by numbers stored in vectors. Various chain growth schemes were tested. The results suggested that the carbon chain growth process could involve the stepwise additions of both one-carbon and two-carbon units.</p> / Doctor of Philosophy (PhD)

<p>This thesis deals with the following four topics: 1. Multivariate statistical methods are used to analyze data from an industrial batch drying process. Principal Component Analysis (PCA) and Partial least-squares (PLS) methods were able to isolate which group of variables from the initial conditions and the process variables were related to a poor-quality product. The use of a novel approach to the time warping of the trajectories for batches, and the subsequent use of the time-warping information, is presented. 2. In the procedure to monitor a new batch using the method proposed by Nomikos and MacGregor (1994), an assumption about the unknown future samples in the batch has to be taken. This work demonstrates that using the missing data (MD) option and estimating the score with an appropriate method are equivalent to the use of an adaptive-expansive multivariate time series model in the forecasting for the unknown future samples. The benefits of using the MD option are analyzed on the basis of (i) the accuracy of the forecast, (ii) the quality of the score estimates, and (iii) the detection performance during monitoring. 3. laeckle and MacGregor (1998) introduced a technique to estimate operating conditions in order for a process to yield a product with a desired set of characteristics. This thesis provides a detailed study of the application of such technique in designing the operation of a batch process. The original technique is modified to include constraints and other optimal criteria onto the desired quality and the trajectories. A parallel approach based on derivative-augmented models is proposed to avoid the analysis of the null space. 4. An extension to the work by laeckle and MacGregor (2000) in solving the product transfer problem is proposed. The early technique does not consider all the data structures involved in the problem and particularly the operating conditions from the source plant. The Joint-Y PLS model is presented as an alternative to solve this problem using all the available data.</p> / Doctor of Philosophy (PhD)

<p>A fully-predictive steady-state computer model has been developed for a single screw plasticating extruder. Included in the model are:</p> <p>(i) a model for the flow of polymer solids in the feed hopper,</p> <p>(ii) a variation of the Darnell and Mol model for solids flow in the extruder screw channel,</p> <p>(iii) a modification of the Tadmor melting model for the melting zone in the screw channel,</p> <p>(iv) an implicit finite difference solution of the conservation of mass, momentum and energy equations for the flow of the polymer melt in the screw channel and die, and</p> <p>(v) a predictive correlation for the extrudate swell at the die exit.</p> <p>A temperature and shear rate dependent viscosity relation is used to describe the melt flow behaviour in the model. The parameters in the viscosity relation are obtained by applying regression analysis to Instron capillary rheometer data. Extrudate swell theories developed for capillary rheometers have been utilized in the development of the correlation are the prediction of the extrudate swell at the extruder die exit. The parameters in the correlation are obtained by applying regression analysis to Instron extrudate swell data.</p> <p>Given the material and rheological properties of the polymer, the screw geometry and dimensions, and the extruder operating conditions (i.e. screw speed, barrel temperature profile, etc.), the following are predicted:</p> <p>(i) mass flow rate of the polymer,</p> <p>(ii) pressure and temperature profiles along the extruder screw channel and in the die, and</p> <p>(iii) extrudate swell at the die exit.</p> <p>The overall extruder model predictions have been confirmed with experimental results from a 1 1/2 inch (38 mm) diameter, 24:1 L/D single screw extruder with a 3/16 inch (4.76 mm) diameter cylindrical rod die. High- and low-density polyethylene resins were used.</p> / Doctor of Philosophy (PhD)

<p>This Thesis report on the free radical synthesis and characterization of styrene/acrylonitrile (SAN) copolymers.</p> <p>A wide region of the kinetic behaviour of SAN copolymers has been experimentally mapped. The effects of temperature, initiator and comonomer concentrations on the rate of reaction and copolymer properties were experimentally investigated and discussed in view of the existing theory. Using low conversion copolymers as standards, current copolymer characterization techniques with particular emphasis on size exclusion chromatography (SEC) have been investigated. Polymer/solvent/packing interactions, instrumentation, calibration and interpretation techniques for SEC were investigated and extended to copolymer analysis.</p> <p>This investigation, as part of an ongoing program on the synthesis characterization, modelling and control of copolymers and copolymerization reactions, provides some of the systematic ground work essential to the understanding and eventual modelling of these rather complex systems.</p> / Doctor of Philosophy (PhD)

<p>Polyethylene (PE) synthesis has shown tremendous progress towards the production of polymers with innovative chemical and physical properties as a consequence of the development of new classes of single-site catalysts, including metallocene and the more recently developed nickel-diimine catalysts. This thesis describes the synthesis and characterization of a series of PE materials using a variety of metallocene and nickel-diimine catalysts. The main objective of this thesis work is to develop a better understanding of the influences of polymerization conditions and catalyst systems on polymer properties. A detailed investigation of the polymerization of ethylene by (adiimine) nickelCII) catalysts was first carned out. The catalysts used were ((ArN=C(An)-C(An)=NAr)NiBr2 and (ArN=C(H)- C(H)=NAr)NiBr2; where An = acenaphthene and Ar = 2,6-(i-PrhC6H3). Changes in the a-diimine backbone structure showed remarkable effects on the polymer microstructure as well as catalyst activity. For all the three catalysts, increasing ethylene pressure or reducing polymerization temperature led to a reduction in the chain walking rates, and thus reduced the melting temperature and crystallinity of the polymer produced. A Nila-diimine catalyst, 1,4-bis(2,6-diisopropylphenyl) acenaphthene diimine nickel(II) dibromide was then supported on MMAO-treated silica to produce short chain branched PEs by ethylene polymerization. The supported catalyst gave far lower activity than the homogeneous catalyst. Depending on polymerization conditions, two active site populations were observed during polymerization using supported catalyst; one remained fixed on the surface of the support, and the other was extracted from the support exhibiting the same polymerization behavior as the homogeneous catalyst. A tandem homogeneous catalytic system was also used for the synthesis of ethylene-l-hexene copolymers from ethylene as the sole monomer. The catalytic system employed the tandem action between an ethylene trimerization catalyst, (11 5- CsH4CMe2C6Hs)TiCh(1)/MMAO, and a copolymerization metallocene catalyst, [(115-sMe4)SiMe2CBuN)]TiCh(2)/MMAO. During the reaction, VMMAO in situ generated I-hexene with high activity and high selectivity and simultaneously 2/MMAO copolymerized ethylene with the produced I-hexene to generate butyl branched PE. By simple manipulation of the catalyst molar ratio and polymerization condition, a series of branched PE samples were efficiently produced. A binary catalyst system, consisting of a Nila-diimine catalyst, 1,4-bis(2,6-diisopropylphenyl) acenaphthene diimine nickel(lI) dibromide(l) and a zirconocene catalyst, rac-ethylenebis(indenyl) zirconium dichloride](2), was developed to synthesize a series of reactor blends of linear and branched PEs. The nickel diimine catalyst generated branched PE, while the zirconium catalyst produced linear PE. At various levels oftemperature, ethylene pressure, and Catalyst 2 fraction, PE blends with different melting behaviors were produced. GPC-V analysis of the PE samples showed monomodal molecular weight distributions with narrow polydispersities.</p> / Doctor of Philosophy (PhD)

<p>The interactions of pressure sensitive adhesive (PSA) with paper surfaces were investigated by using peel adhesion testing as a probe. The objectives of this work were to reveal the fracture mechanism of paper/adhesive laminates and establish the links between paper properties and the performance of PSA tapes. Particular attention was given to analyzing paper/adhesive peel curves. It was found that the peak peel force (i.e. the maximum force in a peel curve) was more effective for analyzing peelings from paper than the conventionally used steady-stateforce. Based on this, we developed a new peel data analysis method by which the overall peel behavior of a paper/adhesive combination is conveniently summarized by plotting the log peak peel force as a function of the log peel rate. This approach yielded a generalized peel curve consisting of a rate-dependent interfacial domain and a rate independent failure domain. The force generated at the paper surface in peeling was analyzed; it was found to be proportional to the overall peel force. By varying peel rates, the two types of forces were shown to have a linear relationship for the two tape types and two paper types investigated. This result justifies the use of the easily measured peel force as an estimate of the real force at the interface. Rapid peelings induce paper delamination in which paper is separated into two layers. Microscopic analysis revealed that there are three sub-processes: 1) initially, the top layer of fibers, beneath the peel front, is lifted; but, 2) it must be fractured in order for the fiber layer to be peeled from the paper sheet; and, 3) in the steady-state delamination region, the top layer of paper fibers are peeled from the paper. Processes 1 and 2 only occur initially, whereas delamination (process 3) occurs continuously during peeling. The initiation of paper delamination from the surface was found to require more than double the steady delamination force because of the need to fracture the top fiber layer (process 2). For the first time, links between paper properties and the performance of PSA have been identified by the use of advanced statistical analysis and the newly developed approach for analyzing paper/adhesive peel curves. The paper properties influencing peel force in the interfacial failure domain are, primarily, the paper surface chemistry characterized by oxygen/carbon ratio (determined by X-ray photoelectron scanning analysis) and, secondarily, the surface roughness. The governing paper property in the paper failure domain is the paper internal (Scott) bond strength. The log-log slope in the interfacial failure domain is independent of paper properties, and it is found to be governed by adhesive rheology. Finally, the fundamental research was extended to solve a practical problem. We developed a new peel-based test for paper surface strength, in which the force required to initiate paper delamination when peeling a strip of adhesive tape is proposed as a measure of paper surface strength. This method makes it possible to compare surface strength with other strength properties of paper. Further, this surface strength was found to be independent of peel rate and strongly correlated to the IGT strength (an industrial measUre of paper surface strength).</p> / Doctor of Philosophy (PhD)

<p>Developments in single-site catalysts for olefin polymerization have offered unprecedented freedom in designing new polyolefins, controlling polyolefin structure, and tailoring materials properties. The main theme of this sandwich-style thesis is the synthesis, characterization, and properties of a novel series of polyolefin materials that have unique chain structures and superior materials properties. These polyolefin materials were respectively prepared with a variety of recently developed single-site catalysts. High-strength polyethylene fibers were in situ synthesized Via nanoextrusion polymerization of ethylene with a mesoporous particle (MCM-41) supported titanocene catalyst, Cp2TiCh. The unique nanotube structure prevented the conventional folding of growing polymer chains inside the nanotubes and thus led to the formation of polyethylene nanofibrils with unique extended chain crystalline structure. Further aggregation of nanofibrils resulted in macro-scaled polyethylene microfibers. The morphological properties of nascent PE fibrous materials were investigated extensively using ESEM, XRD, and DSC. Tensile mechanical analyses showed that the polyethylene microfibers produced in this nanofabrication process exhibited tensile strength comparable to those of polyethylene fibers fabricated through post-reactor processing methods. A Ni/a-diimine catalyst, 1,4-bis(2,6-diisopropylphenyl) acenaphthene diimine nickel(II) dibromide, was supported on various mesoporous particles (MCM-41 and MSF) having different nanotube structures to produce short chain branched polyethylenes by ethylene polymerization. The effects of catalyst supporting methods and nanotube structure of the mesoporous particles on the catalyst impregnation were studied. In ethylene polymerization, some active sites of the supported catalysts showed reduced chain walking ability compared to the homogeneous counterparts. The effects of nanotube structure of mesoporous particles on ethylene polymerization activity, polymer property, and polymer particle morphology were investigated. A series of branched polyethylenes with various chain topologies were prepared with chain walking Pd- and Ni-diimine catalysts, [(ArN=C(Me)C(Me )=NAr)Pd(CH3)(NCMe )]SbF 6 and (ArN=C(An)-C(An)=NAr)NiBr21 MMAO, respectively, under different reaction conditions. In addition to topological characterizations using GPC-VIS and \3C NMR techniques, a rheological study was conducted to investigate their unique rheological behaviors. The high molecular weight polyethylenes prepared under low ethylene pressures (0.2 and 1 atm at 35°C) with the Pd-diimine catalyst exhibited extremely low viscosity and typical Newtonian flow behavior, suggesting dendritic topological structures. Changing the polymer chain topology by varying reaction conditions and/or changing the catalyst metal center significantly affected polymer rheological properties. These novel dendritic polyethylenes have potential in such applications as lubricants, printing materials, and polymer processing additives. A one-step polymerization process employing binary tandem catalyst systems, (,,5 -C5H4CMe2C6H5)TiCh/MMAO coupled with [(,,5_ C5Me4)SiMelBuN) ] TiCh/MMAO or rac-Me2Si(2- eBenz[e ] Ind)2ZrChl MMAO, was applied and investigated for an efficient production of ethylene- exene copolymers with ethylene as the sole monomer. This strategy utilized a tandem action between the two single-site catalysts. During the polymerization, the trimerization catalyst, (,,5 -C5H4CMe2C6H5)TiCh/MMAO, trimerized ethylene to form I-hexene, while the other metallocene catalyst component efficiently copolymerized the in situ produced I-hexene with ethylene to form butyl branched polyethylenes. A simple adjustment of the molar ratio of catalyst components, catalyst combination, and reaction conditions effectively regulated branching density in the copolymers. The branching structure of the copolymers was confirmed and characterized using 13C NMR and DSC. This one-step process has clear advantages over the two-step procedure for linear low density polyethylene (LLDPE) production. A binary catalyst system, consisting of a bisiminepyridine iron catalyst [(2-ArN=C(Me))zCsH3N]FeCh (Ar = 2,6-C6H3(Me)z)/MMAO and a zirconocene catalyst rac-Me2Si(2-MeBenz[e]Ind)zZrCh/MMAO, was developed to synthesize isotactic polypropylenes grafted with atactic side chains. The iron catalyst in situ generated I-propenyl ended atactic polypropylene macromonomer, while the zirconium catalyst incorporated the macromonomer into the copolymer. The effects of reaction conditions, such as catalyst addition procedure and ratio of the two single-site catalysts on branching frequency were studied. Copolymer samples having branching densities up to 8.6 aPP side chains per 1000 iPP monomer units were obtained. Novel long chain branched isotactic polypropylenes were produced by propylene copolymerization with a very small amount of non-conjugated diene, 1,7 -octadiene or I,9-decadiene, with a single-site metallocene catalyst, racMe2Si(2-MeBenz[e] Ind)2ZrCh/MMAO. By controlling the amount of dienes in the polymerization system, isotactic polypropylenes with different long chain branching densities were effectively produced. Rheological studies showed that the presence of long chain branching significantly enhanced polymer melt strength and improved polymer processibility. This in-reactor method is more effective and convenient than other post-reactor processes used for producing LCBedPP.</p> / Doctor of Philosophy (PhD)